Rated 5 out of 5 stars
I've abandoned this addon after waiting two years for the promised update.
Instead I've managed to get the same effect as I wanted using the addons 'Classic Theme Restorer' and 'Classic Toolbar Buttons'.
This is an excellent addon, but I'm not willing to use the Development Channel, and this addon has been broken in the main Release Channel for years now.
Nevertheless, it remains the most well-made, most artistically pleasing, diverse and subtle addon for customising the look of Firefox.