SteamOS is designed for TVs and living room deployments and is slated to be "the environment best suited to delivering value to customers is an operating system built around Steam itself. SteamOS combines the rock-solid architecture of Linux with a gaming experience built for the big screen. It will be available soon as a free stand-alone operating system for living room machines."
Besides having "thousands of games", SteamOS will have "significant performance increases in graphics processing" and they are working on audio performance and input latency reductions too. Valve is investing heavily in their Linux work as I've made mention of numerous times now on Phoronix.
Though what's your hopes from SteamOS? High performance open-source GPU drivers? A binary blob-free kernel land? Btrfs by default? The BFS scheduler by default given the gaming system target? Share your thoughts and hopes for SteamOS in the comment thread below.