I installed Windows 8 Consumer Preview on one of my secondary computers to see if it is playable. The kids were puzzled at first, but then realized that movies link works and there are new games hidden behind the Metro tiles.
I agree that Metro UI is more suitable for touchscreen hardware, and if there is no such hardware is present, it is difficult to justify its usability with only mouse and keyboard (although there are some very handy keyboard shortcuts).
I like Windows interface in general and I believe that Windows 8 works better and faster (that I can witness) than Windows 7. Yet, Metro User Interface is not a revolutionary move on PC screen. It is meant to be simple, which is a good approach. But a computer remains a very sophisticated device and Metro UI on top of it feels overwhelming to me, because as a power user I don’t mind multitude of controls and … empty space on my desktop. Empty space on my desktop is inspiring, as it can be filled with anything. Empty space in Metro is not easy to fill.