It's not a big one, but I have come across it a few times when my UI would be much cleaner if I could have 2 x menu bars.
For example, the top menu bar is 100% sticky, but if I click on a button (say Reports menu) then a new tab would open and on the left I could have another menu bar (or a tree) - which in this example would list all my reports.
There are work arounds (eg HTML / javascript operations) but the menu bars are much more powerful because I can put rules on them etc. And it's much easier to manage them.
Just a thought.
