The usability of Metro is there for the tablet market. The people who don't need a PC and have decided they will not use a PC anymore. PCs are complex and confusing to many casual users. We thought it would get better with education, but we still have millions of young adults who grew up with computers yet are completely unable to function with any slight change. It's easier for them, for one reason or another, to completely jump ship to a tablet.

The Metro interface on a PC is designed to stem or reverse that trend. Why jump to a tablet when you can stay with the PC and use it like a tablet? Or better yet, when your tablet IS your PC, and your PC is a tablet. Metro is useful. Maybe not to me, maybe not to you, but we're a small subset of users. There are many who don't tolerate the desktop.