I have had all the PCs in our house on Vista since Vista RTMed. This includes my kids computers, and I like the Vista parental controls (although I wish they were more comprehensive, combining not only allowed hours of use but quotas as well). I recently wanted to run my old copy of the game Creatures, and could not get it to install on Vista. This was sufficiently frustrating that I decided to switch one PC back to XP. With all the stories in the blogosphere of people "upgrading" to XP I thought it would be an interesting contrast to go back.
So on Friday I did this. It's now Sunday night and I'm back on Vista! I can't agree with those people who think that Vista is inferior to XP. XP was faster, I'll grant - noticeably so - but that was with a clean install with no antivirus installed; my Vista boxes all have real-time AV which adds quote a hit, and I expect the search indexing that goes on in Vista also adds a hit. In every other respect I like Vista more. I have a vague temptation to go back to XP on my laptop as I think I could squeeze more battery life out (I only get \~90 minutes but that is with a Pentium-M tablet with discrete graphics, so it isn't that unexpected).
In particular, in the day that I had XP running it froze up three times, I think the problem was with IE7, not necessarily the OS, but this hasn't happened to me on Vista.
The real clincher? Creatures wouldn't install on XP either!
Thankfully I have Windows Home Server running so reverting to Vista was easy; I still had my old backups.