Rated 5 out of 5 stars

Excellent extension.
Means I can fit in all the UI elements and functionality I want without compromising on browsing space when maximised or usability when windowed.

The only issue I have is that when in full screen mode (either via F11 or full screen HTML5 video) the custom ui elements like the Firefox button or the custom close buttons are not hidden (or in the case of the close buttons, exposed even if they are hidden in the settings). Not a major issue, but kinda annoying especially with video.