For those thinking of a Playbook for presentations, it has a nifty little feature. When you output it to a projector or TV, there is an option to lock the output screen onto say your powerpoint presentation whilst on your tablet you can switch to another app (say to get a video ready) then when ready instantly switch the output screen to the video, then you can let that play whilst you are doing something else on the tablet.
It's a really neat feature.