Actually AH plays better on vista then it does on XP. Obviously its system dependent. I have a 6600 on a crap motherboard with 2 gig of PC5300 ram and a 7900GT. With everything set at stock (no OC), default processes running and sliders maxed left FR is pegged at 60 and with V-sync off is about 120/135...
My only real issue was in trying to find the virtual folders I changed some attributes and it ran em across all users/system and hosed the whole system. Literally so badly that it not only hung the reload but hosed my XP pro so badly it wouldnt "roll back"...ened up "F bombing" {reformat} everything and reloading whole box. Which was fine since I wanted to load a linux OS as well.....
1st time in 15 yrs I've busted a box, Vista is not well documented or "logical" in its build. A lot of reasons to stay away from it but all in all if you've got the horses it runs better then XP did out of the gate IMO....