Valve's Pierre-Loup A. Griffais has begun publicly listing known issues with AMD's Catalyst Linux graphics support.

Via this Steam Community discussion page, known issues with the AMD Linux graphics support as it pertains to SteamOS are listed. The page is to be updated as Valve discovers more issues.

The issues listed right now include black/flickering screen when full-screen mode is enabled for certain games, lower performance compared to desktop distributions, and crackling sound over HDMI. Of course, already in the comments are many Linux gamers chiming in with their AMD Linux graphics troubles.