I started using Firefox 3 Beta 5 last week. The new dynamic address bar is great. I just start typing and it quickly searches through my bookmarks and history and offers suggestions that include page descriptions and favicons. The UI is great, as expected, especially the new ability to choose icons from the system theme (I used to have to install an extension to get Tango icons) which finally allows Firefox to have a native feel. The new way of choosing to keep passwords is very user friendly in that it waits until after you have successfully logged into a site before asking if you would like to save the password. Some add-ons are not compatible with version 3 yet, for instance, my can’t-live-without Sage extension won’t install.
Try Firefox 3.