"Those who don't understand UNIX are condemned to reinvent it, poorly." – Henry SpencerOne thing not mentioned in the controversy about ditching Symbian OS is that making an operating system is a very solved problem, just port the whole of Unix and you're done with it. If you want to subtract things from it, you better know what you are doing, 'cos you will get in real trouble.
Android is Linux, which is classic Unix at its core. Mac OS X is a BSD derivative, and BSD is a conformal Unix. Windows 7 is not a Unix, therefore it is a poorly reinvented one. All the Windowzes are the same: perhaps only merely adequate for the current fashion in the world of computing; but woefully inadequate for everything else. I would gamble hard on Microsoft not being able to do better than what they have in the last 15 years.