I've been playing around with Firefox 3 Beta 2 on my MacBook Pro. Excellent browser so far. The Proto theme looks nice and solid, but the main thing is: Version 3 feels much faster than 2. The rendering is faster as is the user interface. And they took the url completion from Opera, one of the things I really like about Opera (my current browser). One other thing which moved me to Opera are the memory leaks with FF (which have gotten much better with FF3 too). So Firefox 3 might win me back. Only missing the splendid bookmark bar syncing in Opera. It just works from home to work while the Google FF plugin for bookmark syncing is awful.