MBL omnidirectional speakers. How do they sound ?

inna,

not sure I'd generalize to that extent.

There are smaller models that might work well in smaller rooms but distance to walls is probably almost always desirable.

I'm sure there there are much less expensive amps up to the task of driving them well.   However, all demos I have heard have been with MBL amplification TTBOMK. 

I don't know why bass integration would be any harder than with other speakers.   

Imaging is different, perhaps unusual, but I'd say the soundstage and imaging characteristics of omni's/radials in general are what distinguishes them.   Each may either take to it or not.   It does take some getting used to, but I find once you do its hard to ever go back.

Heard them several times at the Newport Beach Audio Show.

The smaller 116s in a small room were nothing remarkable.

The 101s, however, are perhaps the best-sounding speaker I have ever heard by a long shot.  They were set up in a double hotel room, driven by big mbl amps and the presence and soundstaging were nothing short of astonishing.  As I changed places in the room the soundstage perspective of the performers simply changed and the soundstage did not collapse as it does virtually every other speaker I have heard.  Detail and transparency was terrific.

I also heard the big Master References in a big room also driven by big mbl amps and using a digital front end.  MBL was only allowing people to stay for one session, so I was sorely disappointed to hear MBL play some joker's Michael Jackson CD, but even then the sound had the most lifelike dynamics, transparency, and speed I have ever witnessed, even if the soundstage was a little diffuse.  I am not a big fan of pinpoint imaging that one rarely hears live and IMO is a studio artifact anyway.  Luckily some other music was played and I heard several that I then bought.

Summary:  If the sound of the two big mbl systems was an A, every other system I have ever heard started at B-.

I heard the MBL "system" during one of my travels in Dubai in a store that looked more like a luxury HiFi supermarket, a few stores down from the Ferrari dealership. The demo room was acoustically optimized and the presentation was simply unreal. That was the only time in my life that I wished I had picked a different line of work, legal or illegal, and could just hand my credit over to the salesman with a shipping address... It completely ruined my ears for music. Madeleine Peyroux's voice has never sounded the same..

Yep it can be an acquired taste in that its not what most are used to hearing at home but once one gets a proper taste of good omni/radial speaker sound, its hard to ever go back and be 100% satisfied. Beware!