partly works, partly broken Rated 3 out of 5 stars
Dont click the 'Reset Toolbar Layout' options, itll just deactivate the menu bar menus, greying them out and youll have to restart the browser to restore them.
Have only tried this on Palemoon 24 (new profile) but expect itll behave the same on Firefox 25, will check later and update if any different.
Also, when you untick 'Menu in Titlebar' and the browser windows maximized, and you have 'tabs on top' set, the tabs should be repositioned to sit next to the Firefox button in the top row, but this addon keeps tabs in the second row, as if the windows minimized.
So if you can live with tabs never being on the top row next to the Firefox button, and remember to stay away from the Reset Toolbar Layout options works fine, and like that when it shows the menu bar menus, will also keep the Firefox button menu showing, the normal way Firefox hides it when showing the menu bar's annoying, this way better