Go get Firefox 3 RC1. Go get it now. I just opened a 700+ post game thread in under 20 seconds (Beta 5 took about a minute). Gmail's lightning fast. The browser starts up almost instantaneously. And all this is on my crappy work network - can't wait to see what this does at home.
As long as you get the nightly tester tools addon , all your normal extensions will work fine (NTT 2.0.2 is compatible with FF3 RC1).