It works fine, it'll get all of your extensions working. Firefox 3 didn't seem to break extension compatibility so it's mostly just changing the flag that won't let them run.

Of course, some of them may cause crashes, but Firebug seems to work without a problem. I'm not running web dev, should I be running it?

Thanks! I'll back up my FF folder and give 3 a try.

Yes, WebDev extension is awesome! http://chrispederick.com/work/web-developer/

Firefox 3 doesn't overwrite Firefox 2. You can choose to run either Firefox 2 or 3, it just won't let you run both at the same time.

Are you saying it uses a different profile?