Man, you people aren't getting it, the existing windows 7 UI, is still there, you can still use the old way of navigating, geez!!!!! It's just now windows 8 has an optimized touch interface, navigating, windows 7 via a touch without an optimized touch interface is non-sense. Taht was the great failure of windows. As to why you want a unified platform, is because, of development, a developer can simply right 1 set of code, and the OS depending on how the USER is interfacing, either via the touch or old standard mouse /keyboard can determine how to display and access it.
This is actually holy grail and if anyone does it right, which I think MS can, you will have a very powerful tool. I used to be a fanboy, blah, blah, brag about how I loved Debian, and lInux, I mean I'm the guy who would change the kernel and found errors and fixed them for my own builds , have written linux drivers, as teenager I was a tool some 10 years ago, and I was like MS is for kiddies, and now that I've gotten older. The bottom line MS is a dayum good OS and does what it's intended to do well, if they pull this off, Kudo's to them, and actually believe they have a better chance the Android and iOS of doing such a thing. And the plethora of windows app which would then be open to the mobile space simply puts it on another planet.
This is a very powerful concept and I don't see how anyone that calls himself a "geek" can't see it. If you are still in your fandom Linux over Windows days, you'll eventually grow up and understand, different tools solve different problems, A wrench is not better than a hammer is not better than a screw driver, they all serve their purpose, to get the job done. Windows 8 as I see it looks pretty darn promising from the video, from the UI experience.