For the life of me, I can't understand why MS didn't just make Metro a shell that could be launched from the regular Windows desktop instead of doing it the other way round. The shell is not the operating system, it's only the UI the OS presents and presumably there could be any number of those. The OS is all the services and systems the OS supports. As it is now, Windows 8 disrupts the traditional mouse and keyboard desktop which will simply lead to no one who needs that upgrading. MS won't mind because it'll still sell all those guys Win 7 and Win 8 will go to all the touch desktops/tablets it was never able to support before.