I suppose 'Windows' is natural to me because it's the operating system that I grew up with. However, I certain things weird.
Minimize/Maximize/Close
It's in the top-left now. What bugs me isn't that. It's that the maximize button doesn't "maximize". It changes its behaviour on application. Sometimes it fills up the screen as expected. Other times it only goes vertical. On iTunes it turns into a mini-player.
Resizing Windows
Reminds of the systems we used at schools where we can only use the bottom corner to resize. That's not a big deal but when I want to maximize the screen and the maximize window button doesn't work. I gotta drag and resize, drag and resize.
VLC Player
VLC Player is easily the best media player on any operating system in my opinion. But on the MAC I gotta write a script to open it up multiple times. Also the player is detached from the window which bugs me. It's almost difficult to click and drag a video.