They've landed "lazy frame construction" which improves rendering performance by an order of magnitude in some cases: http://tinikkel.wordpress.com/2010/05/24/lazy-frame-construc...

Have you tried Firefox 4 betas? (Legitimate question.) It feels significantly faster than 3 on my machines. Much further on the track of a Chrome-like browsing experience, though there's still many areas it can improve before release.

I'm personally waiting on Electrolysis to speed up the browsing experience. Having a monolithic browser, slower or not than separate processes, just makes it feel more sluggish than it is.