About your previous post asking about Rocket League no Rocket League on Steam Machines right now, Windows only but I heard they are planing a SteamOS Release.
On certain PC's that have to use wireless cards (because it's impossible to get an ethernet cable where it is) the speed of the connection dropped a lot, from 50mbps to 3mbps. Followed some video and it fixed it though. Apart from that No issues.
If you want to play games on the tv, build a small form factor PC, install Windows and use Steam big picture mode. Don't get a console. Also if you want to be playing all games don't get a steam machine.