I have been running vista ultimate for about 5 months now, i really like it. The thing i have found with vista is if you dont have pretty up to date hardware, stay away from it. Its just gonna be slow and have support issues, like the htpc in my sig. If i put vista on it, it would be a total dog though it does meet their "minimum" needs. So far I am very happy with vista and do say if you have the horsepower to push it, run it. The thing with most retail boxes is there is a ton of bloat ware (probably XP holdovers that cause instability in vista) and that unless you drop some serious coin your getting cut short in some area of a retail pc. Vista on 1 gig of ram was a bit of a dog, 2 gigs it got better and the 3 i have now it started to really open up. I have also noticed you really need a decent graphics card to run vista. Alot of retail machines run integrated video and vista doesnt like that to well. Sorry about the long rant but its 5:37 am and im tired and saw this. Figured i would throw out my opinion on the whole mess.
Desktop:
Gigabyte EP45-UD3P
Xeon X3220 2.4 @ 3.0
3gigs of PC-800 DDR2 @ PC-800
3 250GB WD SATAII HDDs
Nvidia GTS250
Razer AC-1 Sound card/Onboard sound
24' ASUS Monitor
Laptop:
Macbook Pro 4,1, 2.4GHz
Phone:
iPhone 3G