For people like me, who play games sitting at their PC, this changes absolutely nothing.
The entire Valve push into the living room is incredibly weird.
I believe it was Gabe Newell who talked about how within the next couple of years PC performance is gonna be at a point where your PC can comfortably run two, three, four or more games at once. Heck, my three year old PC can already run my wife's Sims 3 on one screen while I leave WoW running on the other.
The support for streaming games from your Windows PC to a SteamOS system is another step in that direction. I envision something where I'll have a high end PC (call it the home gaming server) without any screen somewhere in the basement and then cheap SteamOS Boxes + Controller in the livingroom, kids room, bedroom, heck on the toilet that will stream content from the high end PC.
Those SteamOS Boxes could even come in the form of something like those Acer Aspire All in One screens with buildin computer. Or maybe like those $50 Android Sticks that you plug directly into the HDMI port of a screen. After all Android is Linux based just like SteamOS and all it would have to do is stream the picture from the high end PC.