There is some good stuff under the covers, from a programming perspective. However, I think the design language of Metro is too restrictive for the desktop. I like to think of the problem as the three little bears of UI. The WinForms bed was too small, it was difficult to make applications that looked distinct. While the WFP bed was too big, promoting applications to look like anything the programmers dreamed -- plus a little scoop of ugly butter. Metro was a good set of guidelines for the phone, when space is at a premium, but becomes too restrictive as precision of the user input increases. What needs to be created, IMHO, is a design language that scale up and down the precision of controller to optimally complete a given task when presented with the constants of the interface. Or something along those lines.
This, except replace "little scoop" with "a whole industrial ice cream tub".
Oh, and of course, the annoying JIT delay in CLR applications. Even NGen doesn't solve that.