Well, the main difference between OS X's full-screen mode and Windows 8's Metro apps are that OS X's full-screen mode is opt-in. You can't get to it except by pressing the full-screen button in the top right of the window, which hints that leaving full-screen mode is also in the top right. In addition, the Dock and the menubar are visible in normal usage, hinting that hovering on their corresponding screen edges will make them reappear (with a visible leave-full-screen button on the menubar). In contrast, the Windows taskbar can't be pulled up by hovering over the bottom; there's no "switch to windowed mode" button at all; and Metro uses screen corners rather than screen edges - which are less discoverable, and with the exception of the Start button in 8.1, the screen corner menus in question aren't visible in normal usage.

There's also a difference in terms of the keyboard shortcuts: in OS X, Cmd+W is "close tab/window" and Cmd+Q is "quit application", and they're relatively commonly used (and easy to use). In Windows, Alt+F4 is much less user-friendly (most laptop keyboards these days don't even let you use F4 without Fn), as evidenced by the fact that users keep on trying to use Esc and being frustrated when it doesn't work.