I downloaded the new Firefox last night. Truly, it is the fastest browser since…well, since Firefox 1.0. I timed it against the heaviest sites I use: ESPN, CNN, and Google Reader and it beat Firefox 2 and Safari by a mile. Since both of those beat Internet Explorer, at least on the Mac side, I think by the transitive property Firefox can claim superiority. I haven’t yet run across any of the functional improvements. Mostly seems to work the same, to me.
Oh, and the upgrade is really easy, too. I installed the new Firefox and it kept all my bookmarks, all my settings, and my cache. It’s early yet, but thumbs up so far.