A friend of mine gave me a Chromecast for my birthday, and I gotta say I found it very nice and full of possibilities. Plenty of Android apps are prepared for streaming to chromecast and there are a few games that proves the potential of the platform too.
I've used the apps from rtve and atresplayer with success (spanish tv), and I am able to stream my own videos with a great quality with videostream (I have the premium account), a flawless piece of software.
I started playing with it last Sunday, I used this repository as a sender and this one as a receiver. It's important to know you need to register your device in the Google Chromecast console (5$ fee) and then you will be able to test your apps in your chromecast before publishing. The receiver has to be in an url available for your chromecast (in your LAN is fine for testing, once you want to publish It will need to be in a public url obviously).
After registering the chromecast in the console and once It's ready, you need to plug/unplug your chromecast (reboot It from Android didn't work for me), otherwise your chromecast sender won't be able to detect the receiver.