I really like Dart too and actually have worked on projects of multiple types (e.g. a game/simulation, parts of a web-app etc.). The just seems right thing that you mention actually resonates with me (in fact, resonated enough for me to teach students in an undergrad course that involved designing and building a web app).

That being said, traction for any new programming language is hard. A programmer's learning time is limited and most programmers would treat it as an investment. In Dart's case, the investment will make more sense if the Dart team could get the VM onto Chrome's release channel (not Dartium/Chromium as it currently stands). I bet that's going to be a hard fought battle, but I believe this would incentivize developers to code in Dart and serve Dart2Js generated js files to other browsers (FF, IE etc.); especially because the coding/debugging experience is so much better than vanilla javascript (I am now prepared for coffeescript advocates to join the fray).

As an aside there might be some App Engine integration that can help the cause. "Specifically, we are working on server-side Dart support for Managed VM" https://code.google.com/p/googleappengine/issues/detail?id=6...