Ars Technica: Windows 8 on the desktop—an awkward hybrid:
The Windows 8 desktop experience is best summed up with one word: frustrating. It takes the already solid Windows 7 experience and makes some valuable, desirable improvements. The Start screen is an effective Start menu replacement. As I’ve written previously, the Metro apps themselves work well with the mouse and a keyboard: writing applications that are equally comfortable with touch and mouse seems possible. All the different pieces that you need for a good desktop operating system are there.
They just don’t fit together well. For tablet users, the whole is probably greater than the sum of the parts, and the individual decisions add up to a slick touch environment. But they’re problematic for dedicated desktop users, and mixed Metro/desktop usage looks like a real mess.