I'm in the US based and I have one. Last year, my roommates and I decided we weren't going to buy cable TV, so it was very useful to be able to stream video off of our laptops. I cheated a bit though, my parents subscribed to NBCsports, so I was able to use their login credentials to stream every Premier League game to my TV via chromecast.
At first I wasn't sure how reliable it would be, but it's quite good, particularly with apps that have built-in chromecast functionality, like Netflix, Youtube, and WatchESPN. This summer we had a viewing party for the USA Portugal game at our house, and I was a bit nervous about the reliability of both the stream and the chromecast, since people would be rightfully upset if they missed part of the game because of it, but it worked out perfectly.
It's also nice if I have a few friends over that I trust with the wifi password, we can all take turns casting videos/clips, and we'll use sites like poolside.fm for background music and video, all without the hassle of having to physically connect our laptops or phones to the TV.
I only have an iphone, so the functionality is limited to a few apps, but as I understand it works quite well if you have a droid.
I think google might see it as a loss leader on their movie sales via google play.
One point is security.
Is google taking this seriously enough?
As I understand it, after the initial setup, the only connection is through your wifi, so the security on your chromecast is only as good as the security on your wifi. This can be problematic if you share a wifi connection, like in a hotel or office building.
That's also an interesting point about Google Play, right now, any video file that's supported with Chrome can be casted, so (though I don't condone it) someone can easily download a video or tv show off of the internet and chromecast it to their TV, for probably not much more difficulty than it would take to download the same video off of Google Play. I wonder if they plan to curtail the functionality in the future.