I'm excited for this. I have a fair sized angularjs app that is getting unwieldy, and having a compiler that yells at me about type problems sounds great. Even if dart doesn't get supported by non-Chrome browsers, I think it could still provide lots of value to developers: it has the same useful type checking as typescript, with some other needed features. It is possible that the transpilation to JS will cause problems, but overall I think it'll be a better dev experience producing better software.