I began using Chromecast about two weeks ago.
Pros are that it works with any Android or Chrome browser with a wifi connection. And once the initial Chromecast FOB is linked to your home's wifi, it's pretty much "one click and you're in" from any other device. So my Maxx, my wife's Nexus, her tablet, our Thinkpad...
The other Pro is that your phone (or tablet or whatever) is only in the game as a remote, so once you've set up the content, you can go about being distracted by Facebook updates and raging on hating Maxx Verge reviewers while Arrested Development plays on your big screen. All your device does is jump in to interrupt if you choose to use it as a remote.
The con of course is limited support. I know more app support is coming, but Netflix, YouTube, Play Store, and Chrome is it for now (I believe). I think there's hope for mirroring -- I'm reading it can be done from a Chrome browser window, but I also saw that issue with Koush and his local streaming app.
So it sounds like, for now, Chromecast "mirroring" will be limited to what you can display in your Chrome browser window.