Love it! Rated 5 out of 5 stars
I like this add-on so much that I'm using it even though it conflicts with the "Hide BookmarksBar" add-on: If you move the mouse to the top across the different bars, the hidden caption titlebar starts flickering (appearing and disappearing rapidly). Also the context menus of the different bars start "wandering" across the screen if the mouse is moved. Doesn't happen if "Hide BookmarksBar" is disabled.
I'm posting this here as your support site requires a Google account, and I don't do Google.
Add March 17th:
The mentioned incompatibility with the "Hide BookmarksBar" add-on disappeared after the latest update (v.2.6.0). Great job, thanks! :-)