I really like the design of Firefox, but I guess the application menu is in an ugly position because when you look, or you guess strange or ugly the menu side, instead in left side, in other words, we can't move application menu and should be possible, mainly Firefox could allow move it to take advantage of bookmark's space, which it could as well have a certain space by default to show correctly menu options or just reverse your position:
It will be interesting as well to reverse your position, although as I say, I prefer to give a space between browser options (like menu, extensions, etc.) and tabs on tabs area, mainly the only disadvantage in Firefox design is tabs touching the left corner of window and I don't worry if tabs will touch the right corner:
