XP's System Restone alone makes it worth the price of upgrade.
As far as hardware support, all of mine has been perfect (and I've installed it on probably 10 systems now, 5 of which are mine, over a very diverse group of hardwares).
You just don't know enough about XP to make it work the way you want it to.
(Which is not to say that I do! But I have a sysadmin friend who's really into it and I bought a pretty decent book on it as well.)