It was announced by Valve engineer Jeff Bellinghausen (via Gamasutra) that native support for the Dualshock 4 controller would be coming to Steam.
Although similar support would be coming to other controllers, Valve decided to start with the DualShock 4 as it shares some similarities with the Steam controller, such as the touch pad and gyroscope.
“Believe it or not, when you use the PS4 Controller through the Steam API, it’s exactly the same as a Steam Controller. You make the exact same API calls, you only get actions, not inputs, and the Steam API takes care of everything.”
This decision will allow PS4 controller users greater control over the customization of the controller’s button layout, and how the touchpad and gyro works. This could mean that the Dualshock 4 might become the preferred controller for use on a PC, that is until the Xbox One controller receives the same support.