Greetings, I'm someone who is using Dart in production I can tell you that is promising and the community is growing.
The only problem I see is that Dart developers are focusing to much in the newer stuff w/o ironing the basics first, for example, the DateTime datatype can't parse this: "2013-08-03 12:00" but can parse this: "20130742", and to me is more important to work in those basics than all the fancy Canvas stuff or polymer.
We don't know the level of compromise Google has with Dart, I'm taking the risk cause I think is worth it.
It's somewhat disconcerting for Dart to merely be seen as "promising", especially given its competition.
It would take a lot of effort to do worse than JavaScript.
CoffeeScript is basically just JavaScript with a Ruby-inspired syntax.
TypeScript is only a very minimal set of improvements to JavaScript.
If it's doing things right, it should be blowing all three of those away with ease, especially given its origin. The fact that its uptake is so slow suggests that it isn't competing against them very well, which I take to be a bad sign going forward.
To make this clear, when I say "Promising" I don't mean it as something vague, Dart is in beta now and it will hit the 1.0 status this year, so start using it and learning it today ain't that crazy.
The only problem I see is that Dart developers are focusing to much in the newer stuff w/o ironing the basics first, for example, the DateTime datatype can't parse this: "2013-08-03 12:00" but can parse this: "20130742", and to me is more important to work in those basics than all the fancy Canvas stuff or polymer.
We don't know the level of compromise Google has with Dart, I'm taking the risk cause I think is worth it.