Forget Sinofsky. He was one guy and W8 has been coming down the tracks for what, four years now?
The blame here lies with Microsoft board of Directors. Windows 8 wasn't some backroom project, hardware spinoff, or specialised division. It was the company's flagship product, its core product, whose success literally makes or brakes the company.
And the board has fubbed it; Bigtime. The whole project was a disaster since its inception, and despite the recession it's very clear that the entire iDink paradigm Windows 8 attempted to hoist on users is so bad, so awful, that ordinary users are literally giving on on buying PCs full stop. A competent board would have been on top of this, foreseen the problems, and had them resolved before launch. We are now 8 months into launch and Windows 8 is a beached whale leading the whole PC industry pod onshore in its wake.
The first thing that needed to turn this around -- before any resigns, Service Packs, interface revamps, or marketing campaigns -- the very first things is that a swathe of the board needs to go. There's a cohort of bankers and industrialist there who probably have no idea how to run their own industries, let alone a computer software company. If my experience with Ireland is any indication, I imagine these directors are serial board hoppers anyway, so they won't be missed.
Microsoft is a software company. It needs software people on the board. Engineers, programmers, computer scientists, etc; with management experience, but who actually know what software actually is, and how it is developed, sold, and used. If MS puts qualified people in charge they can begin to turn the boat around; but they stick with the current shower of corporate BSers at the helm, this whale will stay dying on the beach for a very long time.