W8 makes a lot more sense, to me, if you think of Metro applications as each running fullscreen in their own ephemeral virtual desktops. You don't "minimize" a virtual desktop; you switch away from it. You don't "close" a virtual desktop; you quit the program running on it, and it ceases to exist. (In other words, the solution in W8.0 is either "press Alt+F4 to quit the application", or "throw-your-mouse-toward/swipe-away-from at the top-left corner to open the virtual-desktop switcher.")
It's exactly the same as fullscreen app behavior in OSX, or Gnome; the only difference is that your "native" windowed apps are all limited to living on a single virtual desktop, rather than the user being able to spread them out across several.
In the upcoming 8.1.1 update (or whatever it's called), there'll be an additional UX: throw-your-mouse-toward/swipe-away-from the top of a virtual desktop, and you'll get a sort of title-bar with caption buttons for the virtual desktop itself. That's actually kind of brilliantly-obvious, once you see it, and I hope that idea spreads to every OS.