This is an extremely nice high contrast theme with some class. The FF logo in the corner is certainly the icing on the cake for this masterpiece. The button mouseovers, background, and border stylings are all very pleasing to the eye, but they do not stand out so that they distract you from your work.
Users who are stingy with screen real estate might not appreciate the slight bit of extra space required in the Navigation Toolbar for the FF logo, but I think it is worth it.
Unfortunately, the search box does not look proper when this theme is used with the searchWP (it still works fine, though) addon. Also, the the bars for the inside borders of the search and URL bar look too much like a cursor. The only difference is that it does not blink slowly, so often I find myself trying to type in these bars when the elements don't actually have focus.
Overall, I would have to say this is my all time favorite theme. The author seems really active in responding to feedback, so what little small nitpicks I have will probably be dealt with in the near future. Great Work, Alex!