It would be nice if the Menu Bar could be hidden by un-selecting it in the View > Toolbars list.
This feature is available in Mozilla Firefox and Thunderbird. If the user wants to quickly have access to the hidden Menu Bar all it takes is pressing the Alt key. The Menu Bar is displayed until the next action (autohide) or if Alt is pressed again (toggle).
I don't know if this makes sense under all OSes but it is becoming increasingly used under the Windows OS.
may be useful in netbooks with small screen where every pixel gained can be important
*** Bug 90195 has been marked as a duplicate of this bug. ***
More substantive discussion(s) comment on the later bug resolving this earlier as dupe of that...
*** This bug has been marked as a duplicate of bug 90195 ***