Rated 4 out of 5 stars

> Importing or "falling through" to the
> existing storage mechanism

First thought: a more useful approach might be a one-off export from Firefox, to a keychain. FWIW I would not expect Mac OS Keychain 1.x to include export features.

An assumption: users who prefer integration with keychains may also prefer Sync Services, truth database etc. (in lieu of Mozilla Weave and the like).

This review is for a previous version of the add-on (1.0a6). 

Yes, a one-off is what I meant by \"importing\"; I would expect it to prompt you the first time the extension is loaded or something. This is almost certainly the simplest approach and what I would do first. I don\'t actually think it will be overly difficult other than possibly trying to look for partial match duplicates.