He lost me when he said you have to use the Dart editor to find references. First of all, the whole idea was to bring JavaScript as Dart into an IDE with similar functionality of a C# or Java IDE, such as refactoring, which works like a charm. Second of all, there is a plugin for Sublime 2 http://news.dartlang.org/2013/02/using-dart-with-sublime-tex... and I'm sure there will be more for other editors. But I kept reading and it became clear he hasn't tested tree-shaking or doesn't understand it. Then he says tree shaking is slow, probably not realizing that converting to JavaScript is not a regular build step, and it's not slow. For development, I code and debug on the Dart VM, which has almost no build time.