I love my OSX setup now, but if I was a "non-power-user", I think it would be completely unusable. Watching a typical Windows user try to maximize a window in OSX is pure pain.
Hit the + button: window gets a bit bigger, but not full screen.
Drag the window to the top: nothing happens.
Try to get to the edge of the window, and drag it out: RSI inducing frustration.
Windows seems to dominate as far as basic user usability goes on the windowing front. I would still find it completely unusable without the help of a windowing app like spectacle[1] or slate[2].