Vista is a very pretty XP... plus a little bit more. The feature jump from XP to Vista is so much smaller than the jump from win98 to XP... that I really see it being a tough sell for them. One thing's for sure... if you're in the market for a new pc... wait until Vista comes packaged with your machine. It's what I'm doing at least.
I don't know how vista runs on my computer, Im downloading it now, but from the screen shots I've seen, it has a bit more eye candy than xp, IMHO