I feel that the complete lack of distinction between clickable/tappable tiles and non-interactive ones is a very real problem, and not unlike the sort of thing that pundits have skewered Apple for in the past (the overly-ornate skeuomorphic-esque visual designs of Calendar / Contacts / Game Center, for example).
That being said, I think there's definitely some truth there for a lot of the other Metro hatred. More and more modern iOS apps have a flat UI style that isn't unlike Metro, but you don't see people giving them shit for it.
That's not a tile. Also, the first time I saw that text, I knew I could click it. I can't explain how they did it, but somehow being able to click it was just consistent with how everything else works. That's just me though, supposedly this guy tested with 12 people... and yet he conveniently omits the results for this task... oh no wait! "many users in our testing didn't click this command" How much is "many" out of 12?
First time I saw it was with a touchscreen device and I didn't find out that it was touchable until I had googled how to add more users to WinRT device.
Therefore YMMV
EDIT:
Negative karma for pointing out an opposite experience with a device?
Our opposite experiences just goes to show that UI qualities are subjective, and until someone releases scientific studies (none of this "many users" crap) that go against Microsoft's own user testing, I don't see why they should ditch their Metro experiment.
I really think that a very simple gradient or a 1 pixel wide white/black(depending on background) border around the edges of all interactable elements would go a long long way to fixing this issue without breaking up the UI too much, it might even expand it because just having that distinction gives you another "word" in your visual vocabulary.
Buttons do have a border. The tiles on the start screen have not. Mostly because they're all tappable (but probably also because the background provides separation and thus a border on its own). There are no non-interactive parts on that screen.
That being said, I think there's definitely some truth there for a lot of the other Metro hatred. More and more modern iOS apps have a flat UI style that isn't unlike Metro, but you don't see people giving them shit for it.