Well I would have stuck with XP, but I had the opportunity to get Vista for free (legally), so I thought I'd give it a try.
I was really expecting to be dissappointed with it, so I was surprised when I found I actually like it. I thought it would be terribly slow, but it runs comfortably on my machine with only 768Mb of RAM. It even boots faster too. And once I'd disabled the pointless eye-candy, I found the new features to be really useful.
Having said all that, I'll still be going back to XP. My reason is simple, Vista's too new, and nothing I want to use seems to be compatible with it. My games won't work, programs won't install, and I keep being told I don't have permission to edit dosbox.conf.:mad:
Hard luck Microsoft, you almost had me bought, but then you went and found new ways to screw it up. Maybe I'll give it another try in, say, 2010?