A number of extensions that show they are not compatible with the final release, actually are. I have already found updates to MR Tech Local Install (now MR Tech Toolkit) and Tab Mix Plus. Just google the names of the extensions and you will find 3.0 final release updates for many of them.

By the way, Khan, Adblock Plus works perfectly with 3.0.

The new official add-ons site maintained by Mozilla really sucks and is not up to date.
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"Offer them what they secretly want and they of course immediately become panic-stricken."