I installed (and uninstalled) SP2 beta. Startup/Shutdown times were about the same, but the apps were s-m-o-k-i-n-g!
It's been a few months now, but if I remember correctly, IE8 beta 2 was giving me fits and I had to uninstall SP2 to get rid of IE8.
LoL!
Oh, what a tangled web we weave... 😀
I haven't tried the SP2 RC, but I *suspect* there would be a substantial performance boost - just like the beta!