While we're talking about UI annoyances, here's one from me:

On OS X, how do I get Cmd-Tab to switch windows, not applications? That is: how do I switch from Chrome to my most-recently-used terminal window using the keyboard without bringing *every* terminal window to the front?

Or, in other words, how do I get the Windows behaviour? In particular, how do I get Cmd-Tab, release, Cmd-Tab to alternate between the top two windows?