Surprised this hasn't been discussed. Was in Beta (wasn't aware of it) and now in the current Steam client release. Previously I was using Splashtop which required you to run borderless windowed mode which was problematic for some games. Have tried a few games with Steam's version and it works brilliantly. Lag is barely noticeable - not that I would advocate playing twitch shooters over it. I'm considering building a small Steam stream box for the living room to attach to the TV in there. While I have a 46" TV attached to my gaming PC, my computer chair isn't quite as comfy as my lounge - and the missus complains about spending so much time in front of the PC. Have been streaming games to my notebook over WiFi at much higher frame rates than if I were to run the game natively. Thought the concept of streaming games over the internet was farcical when it was first announced, now I'm convinced it's completely doable.