To add a few more useful links. Language spec[0][1] is available under a free license and they welcome input on it[2]. The 3 top starred bugs in their bugtracker are: enums, non-nullable types, and "await" support [3], though I don't expect non-nullable types to ever be added, but they like hearing what is important to programmers. If there is really a killer language feature that people want, starring it will increase it's chances of being considered.
[0] https://www.dartlang.org/docs/spec/latest/dart-language-spec...
[1] https://code.google.com/p/dart/source/browse/trunk/dart/docs...
[2] http://news.dartlang.org/2014/02/standardizing-dart-1st-ecma...
[3] https://code.google.com/p/dart/issues/list?can=2&q=&sort=-st...
There are lots of intro pages out there to get you a little more familiar with it [0][1][2]. Dart as a language spec isn't all that deep, and it tries to keep things simple and easy to use. A lot of the power I feel like comes from the library and tools that come with the language.
[0] http://programming.oreilly.com/2013/05/dart-is-not-the-langu...
[1] https://www.dartlang.org/docs/dart-up-and-running/contents/c...
[2] http://en.wikipedia.org/wiki/Dart_(programming_language)