Anyone using the Behringer x32

Yes...
It's great.  Recording live shows to SONAR X2 works well on an old-ish laptop still running XP.

I have a Behringer X32 attached to an S16 as the new central interface in my studio. It's connected via Firewire, under Win7 x64, configured as 32-in, 8-out (from computer). I use the 'Aux-in' TRS connectors for my 'boutique' preamps, and all the other XLR-in connections are either on microphones, or connecting unbalanced devices through an ART T8 balancer/isolator. 
 
The X32 has been stable and VERY flexible. I've done all kinds of signal routing gymnastics such as using the X32's internal effects as external SONAR effects, and running the ADAT-out of the S16 as a tri-amp crossover. 
 
The Mackie Control emulation does not work, and Cakewalk support hasn't answered my query about that issue. It works fine in Presonus' Studio One, so there's an initialization/compatibility/protocol problem at the root of the trouble. 
 
In general, it's a thumbs-up.

I just bought one, replacing a Soundcraft 328XD digital console. I really like it. It sounds really good, feels good and looks good. It's pretty complex though, which is good and bad. Good that it should last and do things for a long while. Bad because it'll take a while to really feel confident with the routing capabilities. 
I'm really liking it so far and would recommend it. I did a ton of research before pulling the trigger.
BUT: no midi control of Sonar whatsoever. totally lame. Apparently, according to Behringer, Sonar is the only DAW that doesn't communicate with the mixer. If that's true, Cakewalk needs to fix this asap. They don't want to be known as the only DAW not to work with one of the best digital consoles out there. Yes, recording audio works great with no problems so far, but come on, there nothing like being able to mix in Sonar with real faders and knobs.