Hide the Menu Bar in Firefox 3.6 Beta 5

Firefox 3.6 Beta 5 has a new feature using which you can hide the Menu Bar. This gives your browser more pixels to display the information on the webpage. You need to right click the navigation or menu bar and uncheck Menu Bar item to hide the Menu Bar in Firefox. You can press Alt key to access the Menu Bar whenever needed.

You can achieve the same in Firefox 3.5 using one of the following extensions:
Personal Menu
Compact Menu 2