I downloaded Firefox 3 Tuesday at work to test out, and I was happy enough that I installed it at home. So far, I'm pretty happy: the memory leakage seems somewhat better, and I like the overall look and feel.
The one downside, as usual, is that several of my extensions broke. However, there's a fairly easy workaround:
Updating your Firefox Extensions:
1. On the page for the extension, click the "Versions" link.
2. Right-click on the most recent verson of the extension, and save it to your hard drive.
3. On the saved file, change the "xpi" extension to "zip".
4. Open with your favorite unzipper.
5. Use the text editor of your choice to open the install.rdf file.
6. Search for "Max Version" and change it from 2.0.0* to 3.0.0* and save.
7. Depending on your extractor, you may have to re-zip. WinZip will ask you if you want to replace the file in the archive with the new version.
8. Rename the extension from "zip" back to "xpi".
9. In Firefox, go to File > Open File and browse to the file. Firefox should recognize the .xpi as an installer and bring up the appropriate dialog.
10. Restart Firefox.
Caution: This will work for many extensions, but not all. I was able to use it to update Read Easily, Create TinyURL, Organize Status Bar, and Copy Plain Text, but with Firesomething and Tabbrowser Preferences, something weird happened that screwed up my tab display.
Some related links:
Lifehacker's Power User's Guide to FF3 is useful.
An article on Mozilla's "chief security something-or-other", who's both geeky, good at what she does, and gorgeous.