Could you list a few customizability examples which you could not do on OSX but are possible on KDE or Windows? I am a life long Windows user, used KDE quite a lot, and OSX for the last year, and I love OSX. I wouldn't claim it's more customizable, but to me it's about the same.
Bind keyboard shortcuts to maximize (vertically, horizontally, or both), minimize, restore size, tile/split, move to adjacent desktop. There's a lot I could learn to deal with on Mac, coming from Linux, but it amazes me that this doesn't seem possible without Applescript.
There are tools to do it as people allude to but I can't help but feel this is a square peg in a round whole solution.
When I use linux, I use a tiling window manager, when I use OSX, I use tabbed terminals and fullscreen mode and workspaces.
Also, I should note that the Command-~ functionality which doesn't exist on Windows and spotlight is enough to make me prefer the OSX desktop to the Windows one.
