I too have a pair of Thiel 3.6's and all I can say about the 7.2's is that I want a pair.
I absolutely love them. Liked them better than the Nearfield Acoustic Pipedreams Ref 15 (~$30K), Revel Studio and Salon, and high dollar Dynaudios. Tightest bass I've ever heard - especially at low volumes where the bass beat usually fades away. Had to settle for the CS6's (and give up some of the low bass) because of self-imposed budget constraints. Both the 6's and 7's use a whole lot of power. I have 400 WPC and use most of it - especially when doing the home theatre thing. I've listened to many speakers and always come back to the Thiels - it's purely personal.
I've sold the 7.2's for some time. They are very refined sounding, and all a lot of casual music listerners would likely ever need I think. With some great gear to accompany them, they will do wonders with vocal, insturmentals, light pop/rock/acoustic, orchestral, jazz, etc. On the other hand, if I was a hard rock junkie(of which I partly am), I would steer elsewhere. These speakers, even with a monster amp(Pass X1000's/Krell FPB's/Levinson 333's/Boulder's "chunkies",etc), they won't smack you in the chest or slam you the way other more nimble speakers out there will I feel. I find even the much cheeper NHT 3.3's and PSB Gold's had more snap and punch down low in a passive speaker. Of course, these speakers aren't as refined as the 7.2 in any other area's. Beyond this, you go to more efficient alternative systmes, or active speaker designs for Rock afficienado's, I think.
Besides this, the 7.2's are definitely a more complete speaker than the likes of the 3.6's. The 6's are closer to what the 7.2's can do. You'll get a better speaker in short.
I've upgraded from .5's to 1.5's to 2.3's, and listened extensively to 2.4's and 3.6's, and spent about an hour with 7.2's so far... The one thing I can tell you is this: with Thiel, you get what you pay for. The 7.2 is as better a speaker as one would expect for the given price difference than the 2.3, for instance. As you go up the line, the performance and price increase proportionately. With that as a given, it really becomes about what you personally need in terms of your listening habits; if you do jazz and light classical, the 2.3's will serve as well as the 6's or 7.2's -- but if you want to be sitting front row at a Kunzel/Cinci Pops performance, you'll need 6's or 7.2's and a LOT of power! As always, see if you can find a dealer who'll let you live with your choice for a couple of weeks and see what makes you happiest.