Valve introduced the Steam controller to the Steam users today with a short introduction and a video demonstrating many advantages of the product. 

Experience a new level of precise control for your favorite games. The Steam Controller lets you play your entire collection of Steam games on your TV—even the ones designed without controller support in mind.

Check out the video they released as well as some screenshots of the controller.

Product specification: 

Overview

Dual trackpads 
HD haptics 
Analog stick 
Dual-stage triggers, each with 10° of travel, a magnetic flux sensor, and a tactile switch 
Gyroscope and accelerometer sensors enabling tilt-to-steer racing wheel functionality and other motion-controlled input 
Configurable controls 
Local multiplayer capability, as supported by games 
Wired or wireless (dual mode) 
USB 2.0 via Micro USB port (cable not included) 
Estimated 5 meters of wireless communications range. Actual results may vary. 
Provides up to 80 hours of standard game play using the included AA batteries during preliminary testing. Battery life will vary based on usage and other factors, such as type of batteries used. Actual results may vary.

In-box

Steam Controller 
2 AA batteries 
USB wireless pairing dongle

Requirements

A Steam Machine or other computer capable of running Steam Big Picture Mode, in order to view, edit, save, and share Steam Controller mappings.