The Chromecast is a great product if you know what you are getting. We have a Samsung TV (flatscreen, but no smart TV). We used our Blue-Ray player to stream Netflix movies. However, the Blue-Ray player took ages to open the Netflix app and navigating in Netflix was horrible and slow. The Blue-Ray player was connected to the router through ethernet, so it was not a connection problem.
The Chromecast solved this for us. We use it mainly to make our TV a little smarter. Mostly, we watch Netflix and every now and then we watch some YouTube videos through it. I also tried the Google Play Music function, which works nicely for me, the same goes for Hulu Plus. The app selection is very limited at the moment. However, it is a product that is very much in its infancy, so I am expecting more apps to become available soon (-ish). I am really hoping that Amazon will make its Prime Instant Movies available through the Chromecast at some point. NHL Gamecenter and HBO Go would also be nice.
Setting up the Chromecast was rather easy for me. Make sure you do have a reliable wifi connection, because the phone/tablet and the Chromecast need to communicate over Wifi. Also, the Chromecast will create its own little Wifi hotspot for a short time, so make sure you are rather close to the TV while setting up, so the Chromecast and the phone/tablet can communicate with each other.
I hope the Chromecast technology will make its way into more products in the future. I would definitely get a soundbar/music system that would let me stream my music (plus Pandora, Rdio etc.) directly to a set of speakers, kind of like a Sonos, just cheaper and super easy to set up.
I would recommend the Chromecast to people who want to upgrade their "dumb" TV or to people who purchase most their digital media from the Google Play Store.