On the gaming consumer side:
Hopefully SteamOS isn't really that different from other Linux distros, so that SteamOS-compatible games would run on Ubuntu, etc.
It is just a trimmed down debian based linux distribution with the steam client, Real time kernel patches and a custom compositor, from an applications point of view it is just another debian based OS.
Players should get less input latency and better transitions between the games and the steam overlay. (It does sacrifice some throughput to get the lower latencies though so in some games the framerates are slightly lower than in Ubuntu or Windows 8)
