I have one as well. At the moment there is alot you cannot do with it, but once they release the SDK, it is going to be awesome.
My primary use for it is to use my smartphone to look up youtube walkthrough videos, chrome cast them to my tv, so I can watch while I play games on my laptop. I have also done Netflix, and playing movies direct from my PC (by dragging into chrome) as well, but some videos won't play in chrome due to codecs and whatnot. Of course, this was all before I got a smart TV with most of that built in, but honestly the "cast" button that appears on my phone is easier to use than the smart TV software, so I end up using chrome cast instead of the built in stuff.
Currently only supported apps can utilize the device, but once the SDK is released, any application to stream to it, including winamp, VLC, etc. When streaming from the Chrome browser, there is a small delay, so I don't see it being used for video games just yet.