Very good, but... Rated 4 out of 5 stars

...the "Full screen" button does not work.
Otherwise my rating would be 10.
Failure code in javascript console (every time I press the "Full screen" button):
Error: Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIStringBundle.GetStringFromName]
Source file: chrome://button/content/firefox/script.js
Line: 149

This review is for a previous version of the add-on (0.4.5.2). 

What Locacle

That button pops up a little alert (you can turn it off) to tell the user how to get out of full screen mode. That error indicates that the string for that message could not be found. If you could tell me what translation of Firefox you are using I might be able to get that fixed quite quickly. I know it is there in the English because it works fine for me