What you've described was my experience. I simply have no idea what others are saying sometimes about their experiences in Windows 8 because it simply doesn't line up with how things work for me.
It's bizarre given the incredible advancement and changes in technology in just the last five years, smart phones, tablets, social networks, that a new UI is considered such an impossible thing for people to pick up. Millions of people seem to have adapted to much more change than this in recent years in the tech world.
It is bizzare that Microsoft simply couldn't have left the start menu in place and made an option to bypass Metro. What exactly is gained by forcing Metro? Why not let the user choose how they want to use their own computer? There is obviously a demand for it.
I've been doing business software development for 20 years and while I've seen and heard plenty of complaints about IT changes (introducing change is what I do for living) I can't think of a single person I've worked with over the years, no matter how resistant to change they might have been, is as brittle to it as you're describing.
I work for a big bank and right now the amount of change businesses here are having to deal with is staggering. The Start Menu would be the least of it.
The people you are describing sound like they'd have a stroke if the roll of toilet paper changed.
I think every programmer should be forced to spend a few days a month doing desktop support on their own products (and I say this as someone who has been programming computers since the DOS days).
Surely you are familiar with the principle of least astonishment? Clicking a button and being suddenly and unexpectedly thrust into a foreign and unfamiliar full screen environment violates that principle.
It is also a generally recognized principle in UI design that moded interfaces are bad for the average user. Moded interfaces can be useful for the power user, when designed properly but for the average user, it just introduces the opportunity for mode error. What Microsoft has done is turn Windows into the graphical equivalent of VI except with none of the benefits. Users must constantly switch between two completely different modes of operation.
Frankly, I think Microsoft would do well to make this required reading material for all of their programmers.