FF3 might be ready for the masses, but I doubt the extensions are ready for FF3, many wil not be compatoble.
That's true, though many are. Some developers won't update until a RC. But, the only two I'm really concerned about are NoScript, and AdBlock Plus, and both of them have been updated. Though I don't, you can have both versions installed side-by-side if the extensions are a big deal. Probably more concern for some extensions on Windows, than on Linux. I can't remember...