Re: Poor 2D performance with 8600gt
seventh , flash is terrible under linux (it maxes out one of my cores) and they have the same freq as yours 2.4Ghz. You shouldn't be getting 100% cpu usage tho.
As for general slowness of gtk, you could consider using kde instead of gnome (unless of course you don't like it).
try ubuntu 64 bit it works fine for me. My system works alright but 2d still sucks but it is usable.