I have very limited experience with Chromecast, I just helped friends set theirs up once. It's very cool, but it has no direct interface, so you have to drive the thing from apps on your phone or a pc. Eg. if you want to watch something on Netflix, you'll have to fire up Netflix on your phone/tablet/pc, and tell it to play to the Chromecast.
If you want a nice streaming device, the Roku is fantastic, although it's way more expensive than a Chromecast. I hear good things about AppleTV as well, but those are really only great if you have a very Apple friendly environment (ie lots of other Apple stuff)
