Add to 
Recently I tried to switch to Firefox 2.0 Beta 1 Release Candidate, but I couldn’t switch because most of my Extensions didn’t work on Firefox 2.
But now you can make all of them work on Firefox 2.0 too, just download and install Nightly Tester Tool Extension and restart Firefox. Then go to Addon Manager (Tools >> Addons) and click “Make all Compatible”
Via Ghacks
Written by 
wrote, on July 14th, 2006
This is an excellent tip. I will have to try it out now that I know the extensions will work!