I use Xp on my home desktop. For vista i need a small hardware upgrade, so for the moment i'm XP fan. On my laptop i installed Vista mostly because of the wireless suport. Also i'm using ubuntu linux.. some times.
I'm still using Xp Pro for my laptop, PC, and my family's PC. i like it better than XP and haven't found good reasons to switch to vista yet.
I'm still using XP on my desktop because I don't want to upgrade the RAM on that computer as it's expensive. I currently only have Vista running on my laptop.
XP on my Studio Desktop, Vista on My DELL XPS M1730 and Windows 7 Beta testing version on home Desktop. Must say XP beat them all.
I'm still using XP. Never had vista on my computer so I'm kind of used to XP. Don't plan on changing anytime soon.
I wont be using vista unless i have to, so far xp is great when I need to do something on windows, other wise, Linux Mint is better... btw I used vista for a week before giving up on it