By the way, I don't think you'll get past the mozilla review process with this extension structure. When I wrote one for my job, I seem to remember them being nervous about loading and executing JS from 3rd parties (the thinking being: if you're hacked, suddenly everyone who installed your extension is also hacked, especially as the JS is executed with raised privs.) Not that you're at that stage yet, but I just thought I'd give you a heads-up :)

Nice idea, well executed.

PS: You aren't using the extension yourself? edit: ah you are now :)