There is no documentation, and getting it set up for me was somewhat unintuitive. To get certain effects, it's necessary to install yet another add-on (quite a handy one, as it fortunately turns out) called Stylish. I think it would be better if this add-on implemented all its own functionality however.
Now I'm experiencing one major annoyance. I'm using the "tabs on top" Stylish style, with the window controls on the tab bar. Visualize that I have many tabs open, and that Firefox can no longer display them all in its one row, so has added the horizontal scroll buttons. I most often navigate tabs with the CTRL+TAB / CTRL+SHIFT+TAB or CTRL+PGUP / PGDN shortcuts. When doing this now, Firefox no longer follows when I navigate to a tab off to the right -- so I don't have the ability to close the current tab using the mouse, for example, or to see the current tab's title. That's really annoying to me. ]-:<
Nevertheless, I'm grateful for the interface this add-on's blessed my Netbook with. Thanks! I look forward to seeing further development of this add-on. Cheers.