As predicted, my brain can't handle this demonstration of the Steam Controller.
I'm so used to the current twin-stick form factor that imagining what it must feel like to have a mouse and keyboard emulated on a gamepad using dual trackpads is bizarre. But this showcase of the controller comes across as strangely natural since it's in the hands of someone at Valve who's gotten comfortable with the input method.
There are more videos of the controller yet to come, and Valve is specifically asking for suggestions on what next to play. This video covers Portal 2, Civilization V, Counter-Strike: Global Offensive, and Papers, Please. I agree with everyone who wants to see a platformer.