Hi, I had vista on a separate harddisk for a while wich was a Beta version for feedback purposes. Ran prey on there and hitman blood money with my ax850xt card. Prey had no issue whatsoever and Hitman randomly crashed (does this on XP also so think it's a game issue there) This was done with beta catalyst drivers and that was pretty stable. Never had vista crap out on me allthough i did disable a lot of services... all in the name of science ofcourse
I would think that most newer cards have pretty stable performance in vista but wait for more replies to hear other thoughts on that.