Probably worth mentioning that a look at requirements is a good idea. In particular it requires you have a GTX 650, 660M or higher.
I've had a couple friends message me about this and they were all really excited about it until I pointed that out to them.
I think it could be a problem for nVidia, timing and compatibility is something they should probably work on. I don't know when they're going to release this, I'm guessing sometime this year? Definitely think they should have waited for their 600 series to take hold and be rolling out the next series before they released this.
I hope that is just a temporary requirement. Technically, it doesn't make sense for them to limit it just to the 650 or higher?
Yes and no. It's possible the requirement is lowered as they optimize it, but you have to remember that they're essentially guaranteeing the ability to stream games with whatever they list, so they can't be stingy on that...otherwise people will complain when a game doesn't work and they have a listed card. When streaming PC games, Project Shield is merely acting as a display - the actual processing and rendering (at 720p) is occurring on your PC, thus the need for a fairly decent GPU.
Now, the fact that it requires a GeForce card and doesn't support AMD is clearly by choice, as there has been no word its using CUDA. Whether that's something that can be hacked or not, who knows. I personally think it would behoove them to support AMD cards too, because I doubt any current AMD user is going to switch to NVIDIA just for Project SHIELD, so you're merely limiting your potential buyer base (though it still stands on its own as an Android gaming device, let's be honest, the streaming of PC games is one of the selling factors).