I am very intrigued by Dart mainly the dart2js route, however I couldn't find a 'Who uses it' page. I always find it interesting to see other services that use a technology and what they were able to achieve with it.
blossom.io uses it in production and there has been an interview on infoq.com lately: <a href="http://www.infoq.com/news/2013/04/blossom-dart-switch" rel="nofollow">http://www.infoq.com/news/2013/04/blossom-dart-switch</a>