I just bought a new system, and installed Vista Ultimate. Trying to get your files over is the biggest pain.
I did figure out WHY it was a pain in the ass, and this may help some of you... for me, the entire problem was multiple drives. I talked to someone from Microsoft, and they said that VISTA is supposed to be all security based. If you use multiple partitions or drives, it messes it up. You should buy the biggest single drive you can and do 1 partition, they run terrabyte drives with single partitions on VISTA at Microsoft.
The other thing is RAM. The minimum is 2 GB, but for adequate functionality, you really need 4. 2 GB of RAM on a VISTA is like having 256MB on a XP.
Beyond my drive issues, it's nice to have a live stock feed on my desktop, a clock, CPU useage, Weather, a photo slideshow, post it notes, and it's FAST (but that's due to the new system). I will have to reformat to get rid of partitions on the new Raptor HD, but I think that may solve the issues. VISTA isn't so bad, you just have to have the system to deal with it.