Here's the thing though: it surprisingly also works with mouse and keyboard! You do lose some display density, mind you, but the upshot in size allocated more than makes up for it.
Also it's not just the Metro UI itself and how it works with the mouse that you have to deal with. You also have to deal with switching between what most people will see as 2 separate OS's. I predict a lot of people will be frustrated with this.
I do understand the 2 OS's concern. I do imagine that after a few years and maybe another iteration or two, people will move on from the need for the traditional windows desktop experience and appreciate the same look and feel across phone, tablet, laptop, and desktop. People will be initially frustrated, but even Facebook can't roll out a minor redesign without millions of people freaking out like FB stabbed them in the back.