Several of the new features are shared with SteamOS
Valve has released a new Stable version for its Steam for Linux client, which incorporates a lot of changes from the previous Betas.When a development version garners sufficient changes, Valve promotes it to stable, and the work for the next beta starts almost immediately.
According to the changelog, an auto-detect step for audio outputs when booting SteamOS for the first time has been added, under/overscan and brightness settings have been added to the initial SteamOS startup UI, and support has been added for selecting the user's sound input device on SteamOS (for voice chats).
Also, the device volume is now being reset to 100% when changing the audio device outputs, and an error message is now provided when Steam is unable to adjust system Audio settings from within Big Picture mode.
More details about this latest release can be found in the official announcement. Download the Steam for Linux installer from Softpedia.