Wow all that to avoid loosing some add-ons that aren't compatible with FF 3.0, the main add-ons that are security related work with 3.0 like NoSxcript, BetterPrivacy, Steather, WOT, JavaScript Options (or have updates available).
So I suggest you update your add-ons whilst still using 2.0 so you are as ready as possible , plus many more and that figure will get bigger now FF 3.0 is at the final release version.
I Just downloaded the FF 3.0 setup and closed FF and ran the installation file and no problems, yes some add-ons didn't work but nothing absolutely essential. I checked regularly for updates to the add-ons and regularly there were updates. I still have some that aren't compatible but I don't think it is worthwhile waiting.