Right now we use Dart for the desktop browser optimized version of Blossom and for a bunch of command line/build tools to manage things like building, testing, release tagging and deployment.

We're super happy with the language and platform. DartPad (https://dartpad.dartlang.org/) is a great way to get a feeling for the tool support of Dart (semantic autocompletion, helpful warnings etc).

I'll write more about Dart and how we use it at Blossom (https://www.blossom.co) going forward.