Being able to resize a Metro App/Window and let it float on top of another open Window could be advantageous for certain apps. Similar to Media Player running in the Now Playing mode. Right now to have that functionality you have to have Metro open on one screen so you can see your live tiles. That uses that whole monitor. What if you could just drag that one live tile over by itself and drop it on your desktop. Or resize the open app so its not full screen. You can do Metro snap but that's a bit clumsy and trying to keep it on screen all the time can be a pain depending on what else is displayed on that monitor.