I've heard mixed reactions to the SP through Beta to RC but hopefully it should be OK.
I've been using the betas and its certainly a huge improvement over the First version of vista.
File copying is about 500% faster over a gigabit network connection for me, this was my biggest problem with the pre Service pack builds.
Driver support seems to have been improved as well which is good to see.
This still doesn't mean I will go near vista in a corporate/school environment for a number of years though. I just re-installed XP on my personal laptop and the general day to day speed cant be beaten.
for home use:
XP SP2 = I can play HD video
Vista = I can't play HD video
Unless sp1 changes this then I'm sticking with XP.
RTM is available via Windows Update now apparently. Some users are having to check for updates a few times before it appears.