Never encourage this developer, here's why: Rated 1 out of 5 stars
Dão Gottwald, the creator of this add-on, apparently is the same person responsible for the removal of "about:config" settings that let you customize tab widths. See for yourself: https://bugzilla.mozilla.org/show_bug.cgi?id=574654
Apparently, it's a very bad decision. We now need plugins for each about:config option removed. I am now reconsidering moving to Chome.