I'm saving up to upgrade my PC (AMD HSA on Kaveri + DDR4) because of SteamOS (amongst other things) instead of getting a next-gen console. And I know a few other people doing that as well.
If they try to be on the most cutting edge process node as early as possible (that's available to them), that could make them quite competitive and appealing, especially as all-in-one solution for gamers. I'd certainly consider them myself, too, but not until 2015, and until they jump to 14/16nm FinFET.
I have been using Steam on Linux and once they get a few more titles final (like CS: GO, they already have DOTA) it removes any need for Windows (home life isn't very Office centric).
It's also annoying to have a full desktop PC in the living room. When game streaming lands in Steam I'll be able to move that entire box into my office and then just have a simple front end Steam Machine handling driving the TV. People keep posting pics of the streaming UI but they haven't turned it on yet.
For my "front end" machines I am using 2 Ubuntu laptops with background auto updating turned on, steam in big picture mode on boot, and either an Xbox controller or a Logitech 710. I am thinking those will hold me over until Valve starts publishing the case CAD files and I'll be able to build my own proper machine.