My previous PC was a dual-boot XP 32-bit and XP x64. I used the XP x64 for games, the 32-bit couldn't make full use of the 4 GB memory (max is 3 GB for 32-bit). Games were faster in my 64-bit XP.
I didn't like Vista (had it on my first laptop), but I do like Windows 7 and will stick with it until Microsoft turns away from the live-tile sillyness or I will turn away from Microsoft if the W7 lifecycle runs out. But I expect Windows 9 to be better. Every other Windows version was a miss (98 fine, ME a miss, 2000, well, the count doesn't completely go well, 2000=almost XP, XP fine, Vista a miss, 7 fine, 8 again a disaster).
But it's not only out of nostalgia it's sad to see XP go, for people without a need to upgrade their specs, they need to install Windows 7 or 8 on their old machines just to have a secure system after april 2014. My mother's got my old machine, but I will need to upgrade it or she'll run increasing security risk.