I have been into OSX since Snow Leopard, and by that time, OSX was unquestionably superior to Windows, period.
The recent Windows 8 launch was followed by lots of controversy (where's the start button, c'mon guys!) which I think are misleading public opinion as to who is winning by now.
Apple going deeper into flat design seems not only to follow Google's neat flat design endeavor but mainly to follow what seems what has shown to prevail as the "right" option design wise. And Microsoft has been working for quite a long time on the Metro interface, that basically is a superb flat design showcase.
For myself, I think that this design choice of Apple's design crew implicitly states this Microsoft superiority - at least by now. They have foreseen it, and so everybody needs to catch up.
What do you guys think?