I attended the Goto conference 2011 in Amsterdam where Kasper Lund, the creator of Dart, officially announced Dart. The features of the language grabbed me immediately but during that time it was not mature enough to use in real projects and I never remembered to check back on how the language was doing.
Dart also benefits from having futures instead of callbacks from the ground up. This does not disallow using a callback model, but it does encourage library developers to use the much superior future (or "promise" depending on what you call them) model.
Dart still inspires me as a language - I really need to find a project I can test it on.