iTunes: how to get out of "full screen" mode in Lion?

You must have tripped over the double-headed arrow symbol at the right end of the menu bar. To get back, slide your cursor to the top of the screen to display the menu bar and slide right to the double-headed arrow (now enclosed in blue) at the right end of the menu bar.

Thanks, 4 years later and I got the same issue. 🙂

For iTunes 12.2, the solution is slightly different.

The default (God only knows who at Apple thought this was a swell idea for anything other than a laptop) is for iTunes to appear on first launch as a full-screen window, in its own Space, and without any of the traffic light window controls. To escape this nightmare, once again, move the cursor to the top edge of the screen, and the menubar will appear – but so will the green (size adjust) traffic light control. Click on it, and iTunes should become a window in the same Space as everything else (YMMV if you have two or more Spaces already defined).

P.S. to Apple if anyone there reads this content: Occupying an entire, 27-inch, 5K Retina Display or even an older, 27-inch LED Cinema/Thunderbolt Display with a single iTunes window is a Really Dumb Idea.