Valve has updated the PC version of Portal 2, adding some features which are certainly appreciated. The first, and most important, is the ability to play with a friend in split screen.
This option was present from the start in console, and allows us to embark on a cooperative mode where two players can work together to make progress, now, from the same couch and on the same television.
It also adds support for Steam Big Picture, which maximizes the compatibility of the game with this mode. For those who do not know, Big Picture (which is still in beta) offers a new interface for Steam, more comfortable to use with a remote.