Basically it 'floats' above all your apps/ homescreen, and its movable like those mini apps.
I only have it for a day.. but here is what i found on regard to this app.
1. Finally u can watch youtube, even when the screen is off.
2. Increase productivity, ie.. in gmail app, press a link and open OverSkreen without having to switch apps.
3. It loads website relatively fast
4. It can play flash
1. If you open a second window, and tab to type on the previous window, the top window will cover your virtual keyboard.
2. Websites that does alot of redirects tends not to load.
3. the dismiss and close button on the top left of the windows is too small to press comfortably.