Rated 2 out of 5 stars

Great concept, and it certainly adds a much needed customization to Firefox; however, this add-on is unfortunately unusable in it's current state. (ver. 0.9.5)It's biggest flaw is that it completely overrides all default functionality of ALL toolbars, including the search-bar and the sidebar; and it does so irrevocably, without any possibility to restore previous default behavior for said toolbars.
Setting them to permanent OFF state doesn't help either, as once you use them via their hotkeys ( Ctrl+B for Bokmark sidebar and Ctrl+F for Find as examples) the add-on simply switches the back to Auto-Hide mode.One example of an instance where this can become annoying is when I tried to drag a tab inside the Bookmark side-bar and it disappeared before I have a chance to allocate the new bookmark.
This, and other future compatibility issues could simply be resolved by allowing a toolbar to fall-back to it's original default behaviour when disabling it in the add-on.

Another annoying hiccup is the big blue button which doesn't even appear in my case, probably because of compatibility issues with the multi-row bookmark bar Add-On I also have installed. Instead it just creates a big void where it's supposed to be; this also poses the dangerous possibility of locking myself out of using Firefox's menu-bar altogether.
In my opinion, this button should be replaced with a more innocuous icon, or better-yet a customizable hotkey.

For now I will keep this add-on disabled and hope for a better updated version which will resolve these issues.