[thorax]

I just use extensions.checkCompatibility=False in about:config and most extensions work just fine.

Also, they've changed addons.mozilla.org where most addon authors just have to flip a dropdown box to move support to a new version-- no new upload required. Many authors don't know that, so they wait until the full release to change their support.

FF 3.1 should break very few extensions. Almost none of mine died, though Firebug is particularly sensitive. But I used Firebug 1.3.0 betas just fine for a while on FF 3.1. (My new laptop isn't using FF3.1 at this moment, though.)