If you're a gamer, the upgrade to XP is mandatory. Whilst there are a few games that won't work as well in XP than in Vista, you'll find that on the whole XP supports almost all the games you'd want to play. In addition, it's vastly increased reliability means you'll spend much more time killing things than restarting, a welcome change I can assure you.
I'm not a gamer, but these few lines had me laughing into my bowl of cheerios. As did this:
Whilst content-creators had insisted on all sorts of intrusive features in Vista that made the multimedia experience a living hell for Microsoft users, thankfully with XP Microsoft were able to insist that their customers' needs came ahead of the content creators outdated business model. It's nice to see a corporation like Microsoft stand up to the cyber bullies at the MPAA and refuse to assume that its loyal customers are criminals.
Thanks for the link, tinjaw