I've been using the Chromecast for a few weeks now and I can say that it is a very solid media streaming device. The concept behind it is that you play content on your mobile device, like a Netflix movie, then you play it through Chromecast onto your television. The content is not streaming off of your phone or tablet at this point, it is streaming through Chromecast's built in applications and wifi.
This prevents draining battery on your device. Your phone or tablet is ultimately just a remote that will only use power when you want to wake it up and pause the show, or choose something else to watch.
I've found that it is so easy to watch using Chromecast that I have stopped waiting for the Xbox 360 to turn on, then load up Netflix. By the time this happens, I'm already watching the show over Chromecast.
The YouTube integration is equally well made. Being able to make a TV queue let's you watch a group of videos; my example was a documentary split into four parts. I just got to sit back and not worry about starting the next part because it was already in the queue.
I tested Google Music through the Chromecast and the experience was just as good as the others. The only place where the experience wasn't as satisfactory was when you wanted to stream a video through your browser. I got significant dropped frames. I even turned down the streaming resolution to 480p in order to make it easy to stream. It was only slightly improved.
This being a 1.0 device is actually very impressive. Everything works well and there are really no frustrations to be had. I am looking forward to the added application support that will be added. Things like HBO GO, Vimeo, Hulu Plus, etc. all need to be integrated as well. I only see a bright future for Chromecast and its simplicity. And for $35 there is really no question. Go out and give it a try.