Unfortunatley, my take is that MS has tried too hard to tie up one OS as an "all-devices" product (or line of products at any rate) with a universal appearance for phone - tablet- computer.
Aside of a few oddities, I don't actually have any problem using Win 8, but I find myself spending little time in the metro home screen.
I think that MS had a good concept gone bad with this. I have tablets and phones running Android ICS and Jellybean, and for these devices, it is a good OS (yes, opinions vary!), but then I find Android of very limited use on a tablet with a keyboard (such as the Transformer)...at that point, I find myself yearning for the classic Windows style GUI and interface, better suited for a non-touch screen with a mouse.
Ok, so admittedly I didn't read the whole thread - got pretty tedious after the first couple posts...
My 4 year old can work Metro just fine. Everything he needs to do with it he can. He can swipe to get to the Charms bar to bring back up the Start screen, he can scroll the tiles over, he can select the game he wants to play, he can play many games.. No problems.
I've been using Windows 8 on a Samsung Core i5 tablet for 4 months now as my work system - it took a bit getting used to, but I have no problems finding my way around now. I use the standard desktop interface for work, as that is where most of the apps are. I have a 3 display desktop set up in my office, and things span nicely (although not in Metro mode, not sure why they didn't allow that)....
My chief complaint so far is that in Metro, unlike *every* other mobile OS, there is no Time and Battery indicators on the start screen. How idiotic is it that I have to swipe to get that information? The only other thing that truly bothers me is on a 13x7 screen, there are only 3 rows of tiles - that makes for a lot of side scrolling to get to apps.