The biggest problem with Unity (for ME!!!!) is its performance, I have issues with how it behaves on a dual screen. Otherwise its perfectly fine. It's the OS X dock on the left hand side. To me, Metro is a larger start menu that's faster than the other ones and I don't use the full screen metro apps on my desktop or laptop, although they make perfect sense on a tablet; although I'm sure some people will and it will be fine. A lot of people maximize their windows and use them, so why not give them no chrome and just all window.