And now for something completely different: After updating my OS to Mountain Lion, one thing was driving me nuts:
I just could not drag any window (Chrome, Finder etc.) from my MacBook Pro’s display to my secondary monitor (which I arranged on top of my MacBook Pro monitor). It just was blocked by the menu bar.
I took me a while to figure it out but apparently you have to show a little persistence: Just keep on dragging! At first the window is stuck below the menu bar but then just as the mouse is about to reach to top of the secondary monitor, the window jumps to the secondary monitor as well.
Nice one, Apple!