It has a single dependency management tool (pub), support for Angular 2, and is generally a joy to use.
Material widgets for Angular 2 (the same ones Google uses internally to build Adwords) are expected to be announced at the Dart summit in October.
The sweet thing about Dart is you don't need libraries like Angular or JQuery. I just use the built in Dart HTML methods and they compile down to vanilla JS.
While it is possible to write Dart code without using types (hence "optional") - the vast majority of Dart code is written using types.
The new Dart compiler also provides a "strong mode" which enforces strong typing in order to generate cleaner Javascript code.
I'm not a heavy AdWords user, so I can't say for certain that this represents all of the AdWords UI. But based on the linked interview, it sounds like they replaced a lot of GWT with Angular.
Source: http://news.dartlang.org/2016/03/the-new-adwords-ui-uses-dar...