Now Firefox 3 comes into second beta phase. Previously, many people complained about the Firefox add-on compatibility on Firefox 3 beta 1. Now it is improved on Beta 2. Many popular Firefox add-ons added support to Firefox 3.
For incompatible add-ons, you can use Nightly Tester Tool to force them work with Firefox 3 and they work!
For me, I just want to try Firefox 3 without touching my old Firefox 2 setting. So that I download portable version and trying now. So far, Firefox 3 looks like it will survive memory leaking issue that killed Firefox 2.