QuickTime Player does a very good job of recording your screen, but the controls are non-intuitive and there's a bug when you want to record a display that has an app in full-screen mode. This problem can not happen when you are using just one display. Here's the workaround when you use more than one display.
When you start a screen recording you have the option to click and drag to define the area you want to record or click on a display to record the whole screen. The click doesn't work if that display shows an app in full-screen mode. There's no feedback that you haven't selected the display and, therefore, have not started recording. When you are done and go to stop the recording is when you discover that nothing got recorded. Doh!
The workaround is to start the app not in full-screen mode, start recording by clicking on the display, and then make the app full-screen.
