Yes. He was divisive. Yes. He had failures. But really what you should do is take this for what it is: a successful person talking about success. The real trap is not that he is divisive or wrong about the future, it's that he almost certainly suffers survivor's bias.
Sinofsky's triad model is the epitome of Microsoft beauracracy- I left the company to escape it (I'd have put money on Sinofsky becoming CEO)
I think there was a point where win8 actually cut into MS' sales - and MS has a pretty tight monopoly on the low-end PC market.
And Win8 is where the things Sinofsky talks about - being aware of how ordinary users actually get thing done - were palpably tossed out the window.
In the discussion of what lead to Win8, the perceived virtues of the Mac were monomaniacally pursued. Static design - having an impressive, beautiful look - was everything. Doing tasks was nothing.
And I think earlier MS for all its other evil, had a pretty good record of producing good, usable programs (buggy too but they were careful at finding the features people needed and wanted).
Just look at Windows 8.