I'm not one of those browser benchmarkers, this is just from casual use. Now that I've been on the 3.0 train for a while, using a 2.x build is a little painful--you don't notice the tiny delays between page loads until they are gone...and come back.
I don't care if it's just a visual rendering tweak or actually a performance improvement (a better network interface, a better memory manager, more aggressive caching, etc.)--it doesn't really matter because the fact is, I perceive it to be significantly faster.
Anyway, I think it's safe to go ahead and get the release candidate build. It'll upgrade you to the final copy when it eventually comes out in a few weeks.