(disclaimer: I work on the Flutter team.)

It's true that Dart is an optionally-typed system, and that type annotations are ignored at runtime. That may seem scary at first, but we built an analyzer that statically analyzes your program and gives you feedback (errors, warnings, and hints).

Dart is used at Google to build very big and complex apps, and our engineers use the analyzer in their build/CI systems to check their program. The analyzer is also wired into their IDEs. So they get feedback if a method doesn't exist, or you are trying to pass a variable into a method that is expecting something else.

The Dart team is also working on an optional analyzer feature called "strong mode", which does even more static checking. In strong mode, you can't write code that is incorrectly typed (but, you can still write code that is dynamically typed, if you want to).

Our experience, at least internally, is that as your program matures and grows in complexity, developers appreciate the extra checks provided by strong mode. The win is that it's something you can turn on later, when you're ready. Early on in the program's development, you are probably refactoring a lot and you don't want to bother with strong mode. This scalability is a win for us.

So for those of use outside of Google, it's not a "smooth" environment to work in. I wish we have the tools that you have. Are they available outside of Google?

Yes, strong mode and the Dart analyzer are all available in the Dart SDK. (Strong mode is in development, but it's still quite useful.)

Yes, but do we also get the custom IDE and whatnot? I'd really like to play with Dart, but I hope it isn't a dead-end for non-Google projects.

The developers on this project are using Atom https://github.com/atom/atom/ for their day to day Dart development. They are contributing to the Dart plugin https://github.com/dart-atom/dartlang, and implementing a Flutter specific plugin https://github.com/flutter/atom-flutter-dev. The Dart SDK https://github.com/dart-lang/sdk provides the basic source code analysis tools. All of these projects are open source, on github, and see regular commits.