Very cool concept. It's true that when having immersive or fullscreen games it will not work. But it could be that is the app has an actionbar then show that, otherwise show a drop shadow with the icon and the name of the app.
For people saying that you can't see as much, two points. You see less of the app, but since there is no scaling, it's actually easier to see what the app is. And, secondly, You could have a 2 finger gesture to expand the app, and/or gyroscope tilting or have the middle one be bigger in a slight carousel effect (similar to the dock on Mac, but vertically)