Window management in OSX is easily my biggest complaint. Installing Spectacle (open source) at least gave me back the Windows shortcuts for half screen, full-screen, and next monitor. The full screen width menu system drives me nuts, as with a 27" monitor I have to go 3ft to the left to find whatever non-keystroked command I need. It feels at least 15 years behind to me, especially given their fondness for those big cinema displays.

Apple seems to think I should unitask on a single monitor. That's not how I work, so it's not for me.