I have a Macbook Air and when it first arrived, I thought I'd give Mac OS X a try. One day I lasted! I missed dear XMonad so, so much. Made me appreciate it a whole lot more.
I originally switched because I was so sick of using the mouse to arrange my windows all the god. damn. time.
I decided to give OS X an honest try after Ubuntu started crashing for no apparent reason.
I wouldn't have lasted much either, if a friend hadn't pointed me to a neat little application called BetterTouchTool [1]. It lets you re-arrange windows using keyboard shortcuts.
I originally switched because I was so sick of using the mouse to arrange my windows all the god. damn. time.