I don't understand why someone would learn to use Dart, Coffescript etc when the effort could be put into developing a deeper understanding of javascript.
All I ever hear from developers sometimes is how browser X is breaking standards and then something like this comes along and I can't help but face palm. I'm embarrassed by the relentless pursuit of non-existent perfection from the developer community. Sometimes you just need to get the job done with the tools you have, and and learn to fucking use them instead of pursuing the grail.