One interesting thing I heard about windows 8 metro interface, and why it is being installed on non touch enabled devices with no option to go back to the start menu, is because Microsoft are using it as a form of advertising by association. This is one reason they could be selling windows 8 at low upgrade prices for windows xp users, compared to previous versions, just to get it out there and onto peoples PCs. As it is a similar looking interface on the phone and tablets, your average person with it on their desktop are then more likely to then buy windows phones, tablets and future devices, because it is a familar looking interface and they don't need to learn something different. Phones and tablets are then where they would make their large margins on. Quite clever of them.