I built this thing to test out SteamOS. I am pretty happy with it so far. Natural Selection 2 (which is my most graphics hungry Linux game) runs at a smooth 60FPS on high settings. The Keyboard and mouse need to be replaced, they are terrible.
Game streaming works pretty well at 720p @ 30FPS pretty steadily. My gaming rig in the other room has to be connected via Wireless N... so I don't think the quality is going to get any better than that. But seeing as how that is basically console level display anyway I have no concerns about that.
Some of the pictures have an aftermarket heatsink in them. I had to use the stock cooler in the final build because I wanted to use both RAM slots, and the Zaleman got in the way of the closest one. With an Intel Socket you could choose the orientation of the heat pipes and avoid low profile RAM but that is not an option with the FM2 socket.
So far, even though steamOS is still in Beta, it was VERY easy to install and get going. Got flash working and normal debian repo's added to the source list. I almost never use it outside of the normal steamOS interface though. I did install XBMC incase I want to use it for media... but so far my appleTV has been all I needed for that.
Temps have been alright to bad, mostly that is my media center cabinet though. I plan on installing some temp controlled fans to cool the cabinet at some point but until then I just have to keep the door open while gaming.