Ever since Valve released In-Home Streaming with Steam, I've been utilizing it to let me play all my games anywhere in my house using my Windows 8 tablet. It's pretty convenient when I need to be in a certain room yet want to get in a quick game of Diablo III. (Yes, you can stream non-Steam games too.)
Valve and NVIDIA are teaming up though to take advantage of those GeForce cards and enable hardware encoding for streaming. That means you're going to get some amazing quality in your stream without taxing your computer nearly as much. The CPU is left to do other things and the video card handles it all.
The experience is really great and having hardware encoding with a NVIDIA card helps performance a lot when streaming. Performance was good before this feature was supported. Now, it'll be even better.