UAC is way better. Really improved. Disabling it easy, lowering how much you want it to watch can be changed and such. I haven't found anything so far that I don't like about this OS.
I've had a BSOD that was driver-related (which isn't surprising for beta drivers on a beta OS) but apart from that I've got no reason to go back to XP. In fact, I'm not looking forward to switching back to XP in August. I love 7 too much!