Yeah... Silv is right.
I was going to mention that I am still running Win98SE and could set all my stuff to look just like that (if I REALLY wanted) but personally I dig the plain boring flat colors of the old style.
In any case, XP does not offer much new stuff in the way of features (for most people) as it really just reorganized all the defaults and the look of everything so you have to figure out where everything is again and how to modify all the OS stuff again (illogically they removed the network protocols tab from the network properties window and added a 'network bridge' icon in the networking control panel... more clickin, more confusion. Comming from a win98se/win2k environment, all the extr icons and reordered bullmalarkey made me frustrated with my bro's new computer, and I reverted to my windows98SE again.)
The only things I like about XP is that it has .net framework with it in the newest versions (from what I hear) and they fixed the active dessktop so it's not a memory hog, though you have to go download the upgrade as soon as you install. It seems that there's so many damn upgrades to download that it's really not feasible for anyone slower than Cable/DSL to get a new OS, especially if they've already spent years downloading patches for their windows98SE machine. (I just got DSL in march this year. If I had lived 1/4 of a mile farther away, it would be an other 4 years before I could get it, and I would be stuck on my 56k still)
You need to decide what's really best for your needs, but if all you want is to change your skins and GUI, then you could stay with windows98se and still have the same look. (though, as I don't use skinning stuff, I am not sure how all that works :-p)
Peace.