Microsoft’s Steve Sinofsky has a longish blog post describing the background of how the Windows 8 user interface was designed. He also touches upon some of the decisions Microsoft made for the new OS.
More interesting to me is the brief history of Windows and how the operating systems hasn’t changed much between Windows 1 and Windows 7. That is to say that each iteration of the operating systems has been more about minor style changes in the front and under the hood improvements over the years. Someone could absolutely use Windows 1 if they are only familiar with Windows 7.
In light of this, Microsoft had to make major changes with Windows 8. The notion of a desktop or an operating system seems antiquated in a mobile/cloud era. Really, computers are mostly just on ramps to the internet for about 90% of people today.
I still think Microsoft has a long way to go in overhauling Windows for the future, but they are definitely on the right track. In my mind, Microsoft just needs to keep simplifying the operating system so it can get out of the way of how people are actually using their computers. There are still too many steps to do certain tasks in Windows 8 that should be a single click or more intuitive than they are.