What is the philosophy of Metro and how do you reconcile the old and new UI metaphors? Will we have a dual world or a seamless integration. And what about up and down and back and forth? It seems like Metro is very simplistic in some ways - you scroll on a horizontal plane, but you don't really navigate up and down or zoom in and out. Don't you worry about oversimplifying the UI, turning Windows into a Teletubbies interface a la Apple iOS instead of creating something truly new?
Disclaimer: I think Metro is ideally suited for the phone and quite possibly tablets.