I don't buy many PC games anymore because I got tired of piss-poor quality control and K&M is the most uncomfortable way to play games IMO.
I get tired of PC games only to find that the game crashes contently do to being rushed with the devs basically saying screw you we have your money when it comes to patches.
My biggest beef is with controls, I don't care how accurate you are at counterstrike, I find the keyboard to be a complete mess when it comes to gaming. Movement is a joke with WASD, digital movement in 2008? ugg. then you have hotkey layout that has you tring to remember 20+ hotkeys. For most PC games defeating the interface monster is the hardest part of the game. Before some joker steps in with "just hook up a controller lulz" very few PC games support controllers and even less have good support, things like xpadder to map buttons to keys can help sometimes, but even then most PC games have such a reliance on the mouse to do anything that its too painfull to use an analog stick in its place.
In all fairness, some "games for windows" that are 360>pc ports have propper gamepad support for the 360 gamepad under windows which is awesome, and the poor quality controller monster sometimes rears its ugly head on some 360 games. If Microsoft would push quality control and require gamepad support for all games in order to get the "games for windows" it would be nice, but I guess they don't want to hurt the 360