As far as I know theres really not anything big for SP3, as Micro$oft is going to get XP off the shelves as soon as it can. Although I have heard its going to stick around for netbooks and Vista Business/Ultimate downgrades. Sad that they won't keep it in the Retail/OEM channels but there it is. go to
www.saveXP.com and sign the petition if you think that XP should stay around.