Rated 2 out of 5 stars

Wonderful idea, wished it had worked in my Firefox 3.6.8. Had no effect at all.

This review is for a previous version of the add-on (0.2). 

Are you sure?

I have definitely tested it with Firefox 3.6.8 (and the Firefox 4 betas) and it works on all. Try refreshing the tab (making sure you have unreads) and tell me if your favicon is updated.