I think this is very promising. But what they really need beyond a new interface is some killer productivity applications that permeate the whole experience. So in the Start section there's an inbox for capturing all my thoughts, ideas, things I saw on the web, various media/text for something I want to do at work and then links to some project-style application to get that work done. Added to this search should be absolutely nailed and backups too.
And if Windows 8 could make the whole online security experience far less painful then I don't see why this shift couldn't be very successful. Would love to see this demonstrated with mouse/keyboard (I'm NOT using a touchscreen at a desk though!)