Early this morning I downloaded the bits for Firefox 3.0 Beta 1. I have been using it all day, and I must say, I enjoy what I see. The overall performance of the updated browser is noticeable. I switched from the latest version of 2.0, which I believe is 2.0.0.9 or something.
Pages are more responsive and the fact that the remember password is less obtrusive is a plus. The biggest downside that I see is that even though the code reports having several hundred memory holes fixed, Firefox still consumes more memory than it should. It should not take 100+ MB of memory to display 2 tabs of google.com. But for some reason, it does in Firefox.
Regardless, I do recommend this version over the current 2.0 version. I like the direction it is headed, but it does not contain any dramatic visual changes from a users perspective. I do not see much change to the interface and no big changes to the options dialog.