But they did make the hard decision-- they decided two combine two experiences on the bet that these two experiences and contexts will merge moving forward. Your device should change in context with you, and you should control it. Why would I have two machines when one will suffice? I will have a surface pro, using both metro apps as well as desktop applications. I will flip the cover over when I want to really engage with my device and hold it intimately, at an angle, etc. When I get to a desk, I can plug in my peripherals and I have a fully functioning machine that can use all of the thousands of peripherals that the ecosystem has developed.
As a side note, have you used metro apps on a desktop? They work well, and generally the simplicity and hard decisions made make the experience more visually engaging.