Windows 8 has a whole new user interface. Is there any demand for a Windows with a new user interface? Doubtful. Extremely doubtful.
If they want to try out a whole new way of doing things, great -- go for it. But don't drag Windows along with it. Market it as a new product, so people who want it can buy it. If they don't believe anyone will buy it, or not enough people to create critical mass, then they really must know that they're not going to achieve critical mass by trying to force their current users, who may want new hardware, to switch to a new user interface. The fact that they wouldn't buy it if it were a separate product is a very strong clue.
The sad thing is that they had a product that people reallly wanted, with Windows at its core, but they wouldn't let us have it. Netbooks. I know because I was one of those people.
Netbooks were marvels. Little packages of a computer with a good-size hard drive, a fast-enough CPU to do the kinds of things people would eventually do with iPads. But Microsoft wouldn't let them make machines that had more than a certain size hard drive, or memory, and I assume screen resolution. Which meant that all the innovation and improvement had to take place in battery life. Which happened, until they reached a level where more battery life was irrelevant. The price was truly awesome, you could buy a lot of computer in a very small package, that had wifi built in, for less than $300. At the time this was more than amazing, it was a breakthrough.
Microsoft, which was already facing the Apple juggernaut, had a unique product that people wanted, before the iPad, and they wouldn't let it evolve. Instead they wanted to force people to want a product they didn't -- more upscale Windows laptops that were heavier, had less battery life, and were serious investments at $1000. The netbooks were like popcorn. The were people's third computers, not even second. They should have subsidized those babies, created a huge installed base, encouraged software developers to target this platform, and let the manufacturers move where ever they wanted. And btw, they could have laid off half their engineers, because the OS just has to keep doing what it has been doing all along, nothing more. Faster, on new hardware. And that's all.
These products would have still had to have dealt with the iPad, and who knows, they might still have been wiped out, but the way Microsoft forced them to be anemic and non-improving, they didn't stand a chance against Apple. They were sitting ducks.
Now, they don't have too many options left, but they still have a cash cow. And if they insist on trying out whole new UIs, then do it, but let Windows become a quiet reliable and invisible platform, and do experimentation elsewhere.
Another way to look at it, the people who wanted rock and roll left Windows a long time ago. The people who are left really don't want to think about Windows. Maybe they want to buy some new hardware. And along with that they get a whole new way of doing things. Bzzzt. Wrong move.
The only thing Microsoft has even removed is the start button. There is, at the core of every Windows 8 installation, a Windows OS. You still have access to the desktop.
The only thing I think anyone can truly be upset about is that they made the default interaction the tiled start screen, which if you think about it is just a full screen start menu.
Microsoft has been mired in half-measures and false starts with one of the slowest product refresh schedules of any modern company. This is clearly an attempt to break from that persona and begin entering the modern software paradigm of ship early and often. To that end, I think they will eventually, by default, do what you are asking and make incremental opt-in changes instead of sweeping structural shifts.