What could really knock this one out of the park is In-Home Streaming. Why buy an nVidia Shield and a high-end GTX graphics card when you can stream to the iPad you already have?
Edit: added this to my blog post quoting you.
On the Nvidia side, they added a GPU feature to stream things to their Nvidia Shield tablet (Android based, I think).
quarterto is suggesting that if Valve made an iPad client for In-Home Streaming it could compete really effectively against the Shield, since IHS works with both Nvidia and AMD graphics cards and so many people have iPads already.