Rated 5 out of 5 stars
I've been missing this add-on since Firefox 4.0 was launched, because there was never an update here and just now I realized that there is a newer version in the developer's site.
There are a few other add-ons that do a similar job, but none does it this good and with so much costumization options.
The only flaw I can point is the lack of an updated add-on button, instead of the old status bar icon.
Just hope it gets updated here as well.