[32bitkid]

anecdotally, my mom really likes Windows RT. Watching her use the traditional start menu, or attempting to navigate Windows Explorer to find something is an exercise in pain. She, honestly, really enjoys the full screen start menu -- easier to find the app she wants to start --, the WinRT full screen apps -- doesn't have to remember/think about window/application life cycle management. It pretty much works the way that she wanted Windows XP to work in the first place.

When I use Windows 8, on the other hand, I spend 99% of my time on the desktop, and the transition to a full screen start menu/screen is pretty jarring. But, honestly, as far as the new UI paradigms go, its not that much of a mess... Try watching a Windows user try to use a OSX for the first time. Or vice versa. Or a mac user trying to use KDE.

I think the real world analogy of the OP is a bit flawed. Babies don't instinctually know how to open a door, that is not something we are genetically programmed for. They learn by watching other people do it, and you learn by trying. There is a low penalty for trying to failing to open a door correctly -- sometimes you push instead of pull -- and that is the point of a good user interface. Does Windows 8 succeed at that? Perhaps, but its not a disaster.

A disaster would be a door that killed you if you tried to open it incorrectly.