Aplotdevice I think your idea is fantastic. What people like ^ seem to miss is that change doesn't mean it will be mandatory to use. Apples new gestures are everyone's cup of tea, but I can't imagine going back to double tapping home button only.
It's a great idea because it would allow for app dev's to choose whether to support the feature in their app. Productivity apps would be the obvious best suited ones for such a feature. There are apps that could manage to serve their purpose with only half the screen available (Especially once the iPad goes Retina!!!), like browsers, word processors, video players, twitter, blah blah you get the point.
I didn't reply when you first posted this despite thinking you had a great concept, but it's frustrating when people **** down an idea like this purely because they would choose not to ever use it. There are still people that refuse to accept multitasking (if you want to call it that) on the iPad. Does that mean it's a bad idea?