This comment had me scratching my head. Right off the bat, if you need to run on older browsers, don't use Dart. It's not a secret. Use TypeScript instead. If you need to make a lot of calls into existing JavaScript libs to the point where speed reduction is noticable, don't use Dart. What's so hard to use about js interop? How is it obscure? Throwing out 2MB file size without stating the LOC of the original Dart source is meaningless. I've never noticed long compile times. I do my development in Dart, which runs almost instantaneously, then when all is well, I do a build which compiles and minifies which is reasonably fast. The only thing I can figure is that you're using Dart Polymer, which last I checked, was still in development. My single page app is approaching 10,000 LOC and minifies to about 295K, which is hardly too large. I'm using Dart as a straight replacement for JS and not trying to use the advanced language features, which my explain my more positive experience.