If you're talking about your main rig, no. You could make a small partition and mess around with it I suppose, but you wouldn't be gaining anymore functionality than what you're already getting through the normal Steam client in Windows. You would be installing this on another piece of older or inexpensive hardware to easily expand your Steam library to other parts of the house. I'm sure they'll also offer other apps like Netflix, a web browser, etc., so you can use it as a media hub/HTPC as well. If the game requirements are low enough, you can choose to run the game locally, rather than streaming.
SteamOS is not really intended for your main rig. It's strongest point is that of a console / htpc type of situation, thus the Steam Box. A big part of it is it is running Linux but can also stream your entire library of Windows games from your main gaming rig. SteamOS won't be a viable standalone product until more games come out for it or Linux in the near future ( although, that depends on the person, as I can live just fine with the native Linux games right now ). If you want to play Windows (only) games, then you need to continue using Windows, or set up another box to use as a streaming device.
Thanks for the answers guys. I actually think I know what SteamOS is right now and the best situation to use it.