It works, but... Rated 4 out of 5 stars

when dragging from the top to un-maximize, the window doesn't go back to its original size. It instead fills the screen height and becomes square. GNOME 3.10.1, Firefox 25.

Edit: Updated to 2.5, but still have the problem. Legacy mode checkbox doesn't seem to work properly. Bug reported:

This review is for a previous version of the add-on (2.3.1-signed.1-signed). 

Is "Use legacy mode" checkbox enabled (on preferences page)? It should be unneeded if you use GNOME Shell.

Also, version 2.5 works better (