Legit Reviews posted a review on the Steambox Part 3 ? Installing Windows 8.1 and General System Performance A quote from the article:

Last week we took some time and built a sub-$400 system that was to be dedicated to gaming with the SteamOS, a Steambox if you will. Later in the week, we took a look at the SteamOS, what it takes to install it, and a look at some of the capabilities of the SteamOS. While the SteamOS has some potential for gaming, there are just a number of things holding it back at this point. The two biggest issues I see the SteamOS facing right now are lack of games support, and the lack of additional features. The complete steam library consists of over 9000 game titles which is quite a few games, the SteamOS & Linux however, support only 1495 games at this point. Unfortunately, many of the games that arent supported are the more popular series like Call of Duty (love it or hate, its a popular series). The hardware that I used for the Steambox looks pretty solid per the specifications, but there is limited testing that I can do in the SteamOS and Linux. I was able to run the Unigine Heaven 4.0 benchmark in the SteamOS article here, but that was about it. So to test the hardware I'm going to toss on a Windows 8 install and run the system through an array of gaming benchmarks.

 Steambox Part 3 ? Installing Windows 8.1 and General System Performance @ Legit Reviews