We've got "install add-ons in the background" code finished and in testing. We've got "bypass the UAC prompts" code finished and in testing. We've got add-ons defaulting to compatible with a blacklist for broken ones (reversing from a default to incompatible with a whitelist) coded and it's in testing. We'll be shipping these in Firefox 10 and 11 so the remaining bits are going to arrive very early in the new year.