I don't care about transpilers and still looking for a use case worthwhile for Dart.
Unless Google pushes it, for example as Android language, ChromeOS or whatever might be the language killer application.
I'm not sure Dart is the answer, but I welcome some competition. I think I'd be really interested to see a browser VM that languages could compile to, which would open the door to many languages. (I suppose asm.js might argue that they're this, and there is LLVM.)
Finally, I leave you with .
Roy looks very promising, and I'm hoping it will mature to the point where it can be considered a viable option for production projects
Typescript would've been ideal, but its kind of fake-open-source (no actual development can be seen on the repository, some of the code looks generated, no discussion about the internals or providing an API) and its moving towards having LESS type inference in the name of improving compiler speed, less type safety in the name of... "its too hard to do" I guess. And they still are not releasing anything which might help other vendors improve their tooling (e.g. Intellij IDEA, the second-best contender sucks at TypeScript). And the module system is a total disaster, especially if you're trying to do anything more complicated and CommonJS.
I never work alone, so I only care for languages ALL team members know, have proper support at the browser tooling and are allowed to use by the customers.
 good luck with source maps on mobile platforms