Part one of Steam's press bonanza around the living room is the announcement of a Linux distribution centered around Steam.
I don't feel like the potential feature-set is particularly noteworthy. However, this is probably the big Linux-enters-mainstream-gaming jump most of us have been waiting for because of data collection.
The infrastructure that is backing SteamOS is what gets me excited about its potential. Linux as a gaming OS has always been hampered by the fact that each distro has a relatively small testing pool and a decentralized data collection for things like GPU performance. Previous to this point, Valve has put out some cute infographics about its user's specs and usage, but I think the technology behind that data gathering will be indispensable in shifting Linux from being an 'okay' gaming OS to something that churns out impressive performance on a variety of hardware choices.
My hope is that maybe this will get that that point where we'll have a conversation turn when it comes to APIs. Instead of, "We'll use Dx because it works with Windows", maybe some key developers will go for "We should use OpenGL because it works with SteamOS AND Windows."