No compatible XCode release yet, it seems. Holding off since I can't afford being unproductive at the moment.
You're okay, actually: I've been using the GM for a while and Xcode 4.5 DP3 is pretty good. It's available on the iOS developer portal if you have access. There's a GM of 4.4 in the Mac developer portal too (should be the same build as the final). Both of these are for Mountain Lion.
Also, I think I saw something about 4.4+ no longer supporting armv6, which is a dealbreaker for the few apps I'm still maintaining that needs to be compatible with iPhone 3G. :(