Can I customize the iPad 2 HDMI output or has it just a mirror function? Can someone tell me if I can customize the HDMI output of the iPad2? I mean that the view on the big screen is not just a mirror of the iPad view.
The answer is, it depends on the app that you are using.

Apps can choose to present different content on the external display if they want. For example Keynote can display the slides on the external display and the presenters notes on the built-in display.