Surprised no one has posted this already, but the new 'Firefox release candidate' came out a couple of days ago. It has about 250 bug fixes, as well as integrated tabbed-browsing controls (replaces most of the functions of extensions like Tabbrowser Prefs and Single Window). It hasn't been added to Mozilla's main page yet, but it is on their ftp server.
You can get it
here.
Scroll about halfway down the page and click the one labeled
'Firefox Setup (1.0rc1, en-US).exe 27-Oct-2004 16:12 4.7M'.
Be warned, it will break some of your extensions, but updated versions are already available for most of them.
Also, if you don't feel like messing with it just yet, the final version should be out in a couple of weeks.