Its being released on October 22, ebuyer and aiming to have it delivered to customers "on that date".
I dont know if its better than XP as Ive not ran W7 long enough, but its likely to be better than Vista is for sure and take more advantage of your hardware better than XP and Vista. There are some small drops in performance here and there, but on the whole, I think the pro's out weigh the conns. With all new OS' theres bound to be driver issues here and there, but I believe they will be sorted quicker than what Vista was by a long way.
Im leap-frogging Vista totally. Ive used it at work for 2 years and its shite, esp on exchange.
Some info here is helpful as its updated regularly.
http://forums.ebuyer.com/showthread.php?t=48424