Gotta say its pretty awesome! I can do a whole fully functional web app in about a 80kbs JS library(including embedded HTML for fast loading of different views).
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.
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.
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.