I actually think Windows RT is a bigger problem than Windows 8 itself. It makes no sense — no sense — to have the legacy Windows interface exist there only for Office (and IE). I think Windows RT should exist as a “Metro” only interface and Windows 8 should continue the traditional Windows paradigm, fading out over time.
I think you’re mainly asking though if I think the Metro interface would work on a desktop or laptop PC. Perhaps, though the lack of apps would really hurt there. People would buy those devices expecting them to do what the PCs they’re replacing did. And they would not be able to except maybe in the web browser which is pretty poor.