Me being serious now: Metro is "nice", and it works on mobile devices because it cleanly and clearly displays information, that's fine.
And we've all seen that it doesn't work as well on a desktop.
I think Metro is the right solution for touch devices... although it remains to be seen how quickly the "fashionable" look dates.
However, as a desktop computer environment, not so much.
If MS are going to impose this as the primary environment for all personal computers, then I fear there is going to be another VISTA style rejection by business users, who have a large base of people working with the "classic" environment and who are not going to want the expense (time and money) of retraining them.
I believe this should be a personality mode that can be selected, so that the default environment can be set to match the type of device and application.