If you have moved on to use Firefox 3 Beta 5 (as I recommended) then you know how much speed was left untapped with previous versions of the browser. There are still a quite a few popular extensions that are not compatible however, Tab Mix Plus, being perhaps one of the most general purpose and useful out there.
But worry no more. If you don’t mind the beta-over-beta code you will be running, there is an experimental version of the add-on available for Firefox 3 Beta 5 that seems to be working just fine. This still has not been posted to the official Mozilla add-ons site, so it’s a little gem I had to share. Enjoy.