What version do you have? Assuming you have the edition with FrontPage - 2002 I think, then I personally wouldn't bother. I got meself a copy and the only major changes I was aware of were the new logos - a sort of shiny gradient effect, which looks nice, a couple more fonts etc and light blue taskbars.
Not really worth the money, but at least it looks nice, which is kinda of what Windows XP is all about... :p