Not too impressive, we all knew this was coming. We want details!
Will it use X or Wayland? I know they said X at some point, but it's not like a binding promise. The webpage speaks of audio improvements (better latency etc.) Will this mean Valve will contribute to ALSA/Pulseaudio or are they making their own sound system? Frankly, the last thing Linux needs is another sound system...
Will it use systemd? Will it be compatible with non-steam games and all regular Linux applications? Can it be used as a general-purpose OS or is it limited to only function as a steam client?
Looks like the plan for supporting old Windows games will be to play them on Windows, but give it input from the Steam box and return a multimedia output stream for the Steambox to feed to the tv. Too bad they aren't backing Wine to make that better for supporting old games more directly without the need for 2 machines running. At the least I would like an option to launch Wine + Windows games from the Linux Steam client itself if only to play the many classic games that do already run great from Wine that have no chance of ever getting ported.
Was a bit surprised this first announcement was about the SteamOS, but I guess the general public probably weren't as aware of it as those of us around these parts and come to think about it I guess this is the first official announcement about it from Valve themselves.
Even though it might not be that big of a surprise it is an incredible smart move by Valve. With SteamOS, Steam for Linux/Mac/Windows they are essentially hitting all targets (disregarding mobile, at least for now. Gabe hinted that mobile also was in their plans). Providing that Valve also will be able to offer other services than games this could be a major threat to the Xbox One and PS4.
Think we all knew SteamOS was coming since Michael said Valve was looking for Linux experience and it doesn't necessarily have to be Linux game experience. I wonder what they did to improve graphic performance other than including binaries from AMD and Nvidia. I wonder if they will use BFS instead of CFS.