Rated 4 out of 5 stars
Great idea, it really speeds up firefox!
I've taken inspiration from you add-on and worked out the rougher edges, rewriting it in object-oriented code, adding support for localization, auto-cleaning and icon auto-hiding.
You can find it at https://addons.mozilla.org/en-US/firefox/addon/13878
Feel free to take back all the code you like, I owe you one!