Osirez Tech

http://www.youtube.com/v/DA9Tf48CRTw?version=3&autohide=1&feature=share&autohide=1&attribution_tag=w4WXYpfE31Tj0xjiwb7ZTA&showinfo=1&autoplay=1

Here are some benchmarks comparing Windows 8 to Linux Mint 15 (Ubuntu derivative).  I fully expect Steam OS to perform similarly to these results.  This is my hardware, so your results will vary but should scale according to the components that you use.