Re: start screen
I think you're probably right that Microsoft expected much higher Win 8 adoption, and much less backlash from users.
As for leaving users in the cold... It was Sinofsky's teams that made the most radical decisions and produced the roughest version of the OS. At least at a leadership level, those teams have been largely disassembled. Myerson leads the OS efforts now, but he wasn't part of the team that removed the Start button and menu, or decided users should boot only to the Start screen, or who let the OS ship with such lousy first-party apps, and so on.
Myerson made the comment about the desktop only a couple weeks ago. My interpretation at the time was that he basically meant, "Look, the people who were running Windows the last few years were confusing. Let me be clear: We are not killing the desktop."
He didn't make the point about previous Windows leaders quite this bluntly-- but the point about the desktop was pretty unambiguous. I don't think we can second guess Myerson by pointing to decisions Sinofsky made a few years ago, under a different CEO and different operating structure, and when Myerson wasn't even part of the team. Also, Myerson went out of his way to address the issue. It was a keynote-- so no on was harassing him with questions, or putting pressure on him to say something he didn't want to say. It was scripted, part of the plan. The Ballmer-Sinofsky Microsoft botched Windows 8's release, no doubt. The Nadella-Myerson duo carries the burden of fixing some of these problems, but not the responsibility for creating them.