Valve, it's time for official splitscreen support.
I want everything that exists to die. I want to tear everything I see to pieces and smash it like the freakin Incredible Hulk.
I just spent an afternoon trying to configure Left 4 Dead 2 multiplayer splitscreen. There are guides all over the place, and even a mod that adds splitscreen to the menu. http://www.gamemaps.com/details/5260
Obviously, I want mouse and keyboard to control one player (either one works) and my gamepad to control the other player. (a wireless Xbox 360 controller which works great in other games)
But none of it works. Sure, the level will load so that the screen is split, and you can use a keyboard, mouse and gamepad all at the same time to control the game.
Both on Player 1. And only for Player 1. And never, ever, under any circumstances, ever do you ever get to even begin to control Player 2. At all.
Guides like this one http://steamcommunity.com/sharedfiles/filedetails/?id=197862101 will say stuff like "IT IS NECESSARY THAT YOU SET THE 360 CONTROLLER SET TO PLAYER 2, THIS MEANS THE LIGHT INDICATOR ON THE CONTROLLER MUST BE ON THE NUMBER 2!" but you can't do that. There is no way to get your only Wireless Xbox 360 controller to be set to Player 2 without another Wireless Xbox 360 controller.
You want to convince us that SteamBoxes and SteamOS can be as good as consoles? You need splitscreen support on the Steam versions of Source engine games. The technical work is done, you just need to implement the front-end. Fix this, Valve.