Hello Linux Geeksters. The Valve developers have updated their Debian-based SteamOS, introducing fixes for the sound HDMI and installation improvemnets. 
From the official changelog:
- Removed hardcoded HDMI sinks from Pulseaudio configuration (new from last alchemist_beta)
- Streamlined install process (accept Steam Install agreement, wait for Steam to update itself, Exit Steam dialog) (new from last alchemist_beta)
- Added debian-installer and debian-cd source packages to the repo
- Fixed mouse cursor disappearing in Wargame games by stubbing out all pointer grabs from the modeswitch inhibitor hook
- Fixed hotplugging USB sound devices by re-enabling Pulseaudio dynamic module loading
- Changed PolicyKit configuration to give members of the sudo group admistrative rights (GitHub issue #115)
- Merged Debian GRUB updates
- Fixed kernel updates breaking WiFi on Brix Pro boxes by moving the experimental rtl8821ae driver into a monolithic staging driver (many thanks to Greg KH!)
- Fixed Logitech K400 wireless keyboards
Also worth mentioning, SteamOS got patched to work on dual-boot, even on non-UEFI computers, supporting both AMD and Intel GPUs.
The story so far:
As you may know, Valve, now a member of The Linux Foundation, has initiated some ambitions projects: the SteamOS, a Linux operating system optimized for gaming, the Steam Machine, a gaming colsole that will run with SteamOS and the Steam Controller, a game controller specially designed for SteamOS and the Steam Machine. A demo video of the Steam Controller can be found here.
The first Beta version of SteamOS 1.0 (which has been released in November, 2013) is a customized Debian Wheezy system, running on Kernel 3.10.11, back-porting fresh Nvidia, Catalyst and Mesa binary drivers, uses SysVinit as the system’s default event manager, a personalized GNOME 3.4 as the default desktop environment for the Big Picture mode and Xcompmgr, a lightweight graphics compositor.
While the Nvidia graphics cards were supported by default, Valve has recently patched SteamOS to officially support both Intel and AMD GPUs.