Rated 5 out of 5 stars
I use Ubuntu and disable icons in menus, mostly because its broken and looks like crap. However disabling icons in menus system wide affects Firefox, as in it makes Firefox look like crap (not to mention that the icons in Firefox are actually quite useful).
Enabling this add-on brings all the Firefox icons back even if they are disabled for everything else, which is awesome. Plus it fills in lots of blanks. Now instead of a bunch of missing icons there's only a few. So thanks :)