So how many use MM cartridge and intend to keep it that way ?

Not in entry level set-up.
I currently have Goldring 1042, Nottingham Spacedeck/Spacearm, and might try The Cartridge Man or some vintage cartridge later.
I keep a Grace F9R on an extra VPI arm wand and use it from time to time, don't know that it isn't nostalgia that keeps it in rotation or that it really does sound that good. I will always have one as well as my XYZ Universe and my Mayabi Standard.
I am raising my hand.
But I also run a ZYX UNIverse and love it too, on a different turntable.

I have never had a turntable with anything other than an MM cartridge so I have to ask, is there THAT much of a difference?

IMO, Every single cartridge brand and type, regardless of how it works (MM, MI, MC), sounds at least a little bit different from any other cartridge.  Whether that difference is worth worrying about is subjective.  Among the different types, I have found, thanks to Raul et al, that I prefer MM and MI over all but a very few MCs.  ZYX UNI is one of those MCs I like a lot.  Funnily because it displays some of the best qualities of MM/MI.

Inna, Makes sense to me to have four turntables, actually.  But I am nuts.
Albert has two tables and four arms, all MC cartridges, though. Makes sense to me too but probably would be too much for me. Two cartridges ready to play at any moment would be enough for me, I am quite certain.
Many of the vintage MMs do indeed sound excellent. Thanks to Raul, lewm, timeltel, nandric, and others I got to experience some great ones. My favorites: Signet TK-7LCa, Micro Acoustics (electret) 2002, 530mp, 3002, Sonus Gold Blue, and Empire 4000D/III.

Nothing is wrong with you, you just haven't reached those levels of happiness yet.
I switched from a ZU DL103 MC to a Gold note Vasari Gold MM cartridge.  One of the best moves I have made.  On my Prime, it sounds fantastic.
@stereo5...thanks for the heads-up on the Gold Note Vasari Gold MM. I’m always looking for a new cart. Never heard of this one. Can’t believe I missed Jeff’s write up in ToneAudio about it.

I'm guilty I suppose as I have three MC's and 8 MM's. What's even worse is that my go to cartidge for MM is a Nagaoka MP11 Boron.  It's like the MM equivalent of my 1966 Denon 103 (retipped many times).  
But then there are so many favorites from Audio Technica, Ortofon, Shure, Dyna, Decca, Sonus, Grace,etc. 

A better question would be 'who could live with just one cartridge?'

Now that I'd like to see. 

I am quite sure I could but not sure with which one, ideally. However, at least with my current table/arm and the rest of the system, this would more likely be MM. Yeah, I think I should try that Cartridge Man cartridge at some point, not exactly free even from the UK. Nagaoka 500 will be too smooth for me, I guess, I like some bite to the music in addition to the coherent flow. I am a tape man so naturally I want to come as close to the tape as possible.
I was a ZYX owner too, upgraded from silver coil Airy III to copper coil Premium 4D model. When the cantilever on my 4D was stupidly broken by accident i was shocked by the price of exchange programm to get the new 4D instead. Even with very special offer from US distributor it was definitely too much for me, i tried to save money for exchange to get my Premium 4D back to work. You know that you can’t rebuild ZYX to original specs nowhere in the world when the cantilever is broken. So they are actually exchange broken cartridge to completely new cartridge (no chance even for retip by Nakatsuka-San, only exchange to a new cartridge if you ship your broken unit back to official distributor). This is extremely expensive cartridge to live with and to use everyday! When i realized the situation i decided to try some of the best vintage MM cartridges, because before i bought my ZYX carts i owned rare Technics EPC-100c mk3 and EPC-205c mk4, but i was influenced by MC propaganda, lol
This story is about 4 years old.

Now i have more than 20 rare vintage cartridges on hands and all of them are top of the line models. About 5 of them are rare vintage MCs, the rest are MM/MI/MF.

Most of those vintage MM cartridges are even more attractive than my ex ZYX premium models. Some of the vintage MCs are still waiting my audition, but i hope i will not disappointed by my FR-7f, Ortofon MC2000 arrived this month.

My goal was to spend in a couple of years similar amount of money required for one single ZYX exchange (which is about $3000), but to try as much as possible top vintage cartridges. The idea was to try great cartridges in my system on many tonearms to find out what i really like, based on my own experience.

I would never buy single MC cartridge even for $1500 and will avoid any MC cartridges in $2000-5000 price range. Simply because $500-700 vintage MM cartridges are even better! And vintage MC under $1500 are also better than modern $3000-4000 cartridges. This is my personal opinion, of course, but at least i tried many cartridges to make this conclusion for myself.

I use Technics SP-10mk2, Luxman PD-444 and Technics SP-20 turntables. My current arms are Reed 3p Cocobolo "12inch, Sony PUA-7, Victor UA-7045, Luxman TA-1, Lustre GST-801

I’m pretty sure that vintage MM cartridges are must have for any audiophile to compare modern MC sound to the lost vintage MM sound. Most of the mega rare vintage MM carts are still under $700-1000 used, but even used $300-500 vintage MM are gian killers if you know which one to choose, thanks to the audiogon contributers, loads of great stuff was discovered over the years.

I don’t care about modern MM cartridges!

My former comrade Don become my ''brother Don'' so since some

time now we consult each other about  new purchases. He bought

two display cases for each of us such that each cart in them has

its own headshell pre-adjusted according to the Mint tractor and

ready to be exchanged in 10 munutes time. We don't use the

expresion ''best cart'' but ''first row'' cart. My first row consits of:

Allaerts  MC 2, Magic Diamond, Benz LPmr, Urushi Blue Sky,

Ikeda 9 TT and Phoenix and the second row of the first display

case : FR-7 fz, Ikeda 9 Ciii, Miyabi standard, ZYX airy 3 and

Nakamichi 1000. (chakster my ZYX got a new cantilever/stylus

combo + new suspension by Axel for about 500 euro).

I don't know exactly how many MM carts I own but my ''darlings''

are ADC TRX 2 (beryllium) and JVC X-1, mk 2.

I own two TT's and 5 tonearms. On my Kuzma Stabi Reference

I use the Reed 3 P (12'') and Sumiko 800 (alias ''the arm'').

On my second ,Technics SL 1000 (aka SP 10,mk2 + Obsidan

plinth) I use two of my FR-64 s kinds (silver and cupper) and

Ikeda 345 .

Sort of...  My phono pre is built in to my McIntosh C220 preamp, and it is MM only.  I have toyed with the idea of a Step-up Transformer, but the expense of a good one is daunting.  I run my modded Thorens TD-166MkII with 2 pickups, each on its own 'arm wand: A Denon  DL-160 (which is a High Output MC, so technically not a MM), and an Ortofon OM-30 Super.  I have an OM-40 stylus in waiting for when the OM-30 is finished.  Yes, there are differences between the Ortofon and the Denon, but they are mostly subtle.  I spin some vinyl, but I have to admit that I mostly digitize my vinyl for use on my server and in the car (an ongoing 10+ year process).  For this purpose, my vinyl rig is more than adequate.  I get many compliments on my needle drops from fellow audiophiles, so I guess I am doing something right, even with my not-so-high-end rig.

ZYX airy 3 and

Nakamichi 1000. (chakster my ZYX got a new cantilever/stylus

combo + new suspension by Axel for about 500 euro).

This is no more a ZYX, because the original ZYX cantilever/stylus combo is way different from anything else on the market if you saw them under microscope. At the same time i saw Axel's cantilever/stylus combo and compared them. I have contacted various retippers when my 4D was broken to see what they can offer. I think it's critical for ZYX cartridges and that's why they are what they are (unique in it's own class). 

Why do you not care about them?

I think i already explained in another thread not so long ago.
BTW the Cartridge Man is just reworked Grado ? I would advice to check Joseph Grado (signature model) XTZ before buyin' Cartridge Man. The XTZ was TOTL and the price in the 80s was $750. 

I am a tape man so naturally I want to come as close to the tape as possible.

Then you should check this TAS article (from the golden age of analog) if you haven't seen it before. Those guys comparing digital master tape, analogue master tape, direct-to-disc lacquer and the "live" mike feed; the report consists of a long conversation among J. Boyk, Keith Johnson, Doug Sax, and J. Tammblyn Henderson. 
"What cartridge, what exotic audiophile wonder of disc playback, was producing these marvels? What cartridge could have the "lowest distortion of all," "uncanny" resolution, better than master tapes? The answer is (I wish I could put a page turn here): The Stanton 881 Mk II.

The scene shifts. Kavi Alexander, auteur of the remarkable Water Lily Acoustics series of analogue vinyl discs, is monitoring disc production by comparing test pressings to the master tape. What cartridge is he using? Another moving magnet, this time the Technics EPC-100 mk4...

Audio-Technica AT-ML170 is very similar, and very close to the actual sound of the tape. In this comparison, he says, virtually no moving coil does so well; most have seriously apparent colorations."   

Personally, i prefer the AT-ML170 (i have a spare) and AT-ML180.   

Dear chakster, the logic of identity relation is not easy to grasp

but the rule is that the same name refer to the same object. There

are however different names which refer to the same object but

we somehow have no problem with those. Say Vienna , Wenen,

Bec, etc. refer to the same city in Austria which Austrians name

Wien. The logical rule is then that whatever is true about Vienna

is also true about Wien, Wenen (Dutch name) and Bec (Serbian

name). So your statement ''ZYX is not ZYX'' is at least confusing.

I think that your meant ''the old ZYX is no more the new ZYX''.

The old Nandric is, alas, also no more the young one.

I ever started a thread about ''irreparable'' cartridge but nobody was

interested. My reason was my Sony XL 88 D as well the ZYX.

Their body is made from ''plastic'' which is glued together so

there is no entrance to the inside parts. The Sony was probably the

first cart which was  ''potted'' so nobody was willing to mess with

this cart. Axel try for two years and give up. But he fixed my ZYX

by cutting some parts from the body in order to get access to

the generator and suspension. If your new ZYX is even more

difficult to fix or rather impossible to fix then I am sorry for you

considering the old as well the new prices for both ZYX kinds.

Even if any of those ZYX is made and delivered from Eldorado

I would not even dream to buy one (grin).  

I bet, some MC people are reading this and having fun.
I don't belong to any camp. Kavi's opinion does carry weight for me.
No, I haven't read that article but I will, thank you.
I know nothing about The Cartridge Man, it is just that it is not one of more popular choices, which may mean different things.
Look at the Cartridge Man, then look at the Grado
Compare the prices, you'll be surprised. 

I have a Soundsmith Aida MI. I have had the Dynavector 10x5 and had the 20x also. Heard some other MC all under 2k. Always thought they sounded thin and ultra detailed but lost the musicality.

I think my current keeps most of the detail but has much more body and musicality. Plus it does not just wear our leaving you a huge bill. I am sure someone will say you need to spend at least 3k to hear what good MCs are all about. My response nah I good. 
$2k Lyra Delos, which used to cost $1k two years ago from the UK, is where it might make sense to start. Or Ortofon Cadenza Bronze, $2.5k. Then there might be Kiseki Purple Heart and Transfiguration. 
Still, coherence, impact and weight of a good MM and MI is something that is not easy for any MC to match, as I understand it, if possible at all. This will most likely keep me in the MM camp forever. This and the cost of better MCs. 

Sad about the price of the ZYX Universe series.  The original UNI was about $4500 in the US.  Then the UNI II was introduced as the new greatest ever, for about $8000. Now we have UNIs with really complex suffixes, for around $9000+.  I bought my original UNI for about half its original cost, $2000.  It's the most I have ever spent on a cartridge, but I do feel it was worth the price.  However, I am not a buyer for the $9000 version.
Dear @inna :  """  $2k Lyra Delos, which used to cost $1k two years ago from the UK, is where it might make sense to start. Or Ortofon Cadenza Bronze, $2.5k. 
Still, coherence, impact and weight of a good MM and MI is something that is not easy for any MC to match """

maybe a misunderstood by your part and maybe for other MM lovers. 

In my experiences any LOMC good design has all those characteristics you mentioned and several others, even characterisitcs that no MM can match. If some audiophiles think different about only can means that something is wrong in their room/system overall set up and/or in their live MUSIC knowledge levels.

Did you heard in your system the Delos or the Cadenza Bronze?, you own a pretty decente analog rig that can makes a good job with a LOMC cartridge.

Regards and enjoy the MUSIC NOT DISTORTIONS,
1) Grade gold 1 with paratrace tip which I potted with wax.
2) Shure m95he
3) Empire 4000 d/iii
4) Empire 875
5) Rega bias 2
tables are a Union Jack rp3 Audiomods arm. And an Empire 208 Sme m2/9.

I love the body and weight  you get from some mm and mi cartridges, plus mid range timber. A good stylus can make a world of difference. I did own a Cartridge Man for a while, but needed some extra funds at the time so sold it. It was smooth with a incredible sound stage and detail, but did not produce the bass slam I like in my system. 

I have only used Grado carts. I briefly tried a Dyna 17d3 through one of Bob's Devices. I much preferred my Sonata. I thought about 2500.00 retail for the step up and cart combo would give me a good mc taste. Price not including the IC. I currently use a Reference1 that sounds really good to me. I think about trying some of the above mentioned vintage mm. One day I hope get to them. For now my new Belden 8402 IC has made for some really nice music coming out of my system. Iow, I don't plan on messing with a cart change anytime soon. 
When I hear someone say "bass slam", I don't quite know how to take it. Either they are talking about bass that should be reproduced as recorded or about exaggerated bass that they like.
'Messing' with interconnects can be very beneficial even if not exactly free.
It's true sometimes it's an exaggerated bloom in the bass region, but other times I begin to hear more detail and a stronger mix from the bass lines. Example would be Zeppelin JPJ and stand up bass in jazz even from a very low cost cart as a Shure m35x even if it's lacking in other areas.

I can list some of the very best MM/MI/MF from my own collection:

Glanz MF61
Grace F-14 Exellent (w/F12B stylus)
Grace F-14 LC-OFC
Garrott P77 
Joseph Grado Signature TXZ
Pioneer PC-1000 mk2
Stanton W.O.S. 
Victor X-1II
Technics 205c mk4 
I run two TT's, one's setup for MC and the other MC or MM but mostly MM.   Which I use is based on the LP I'm playing.  Each type of cartridge flavors the meal in it's own unique way.  
I'm weird, I use old Pickering and Stanton cartridge bodies (I have quite a stockpile) with new JICO Shibata stylii in 'em. Sounds right to me with my old jazz records. I've owned several MCs and other MMS.