[epidemian]

LiveScript is more like a functional sugar coat over JS, so it preserves most JS core semantics. Especially strict evaluation and duck typing. Because of that, i think it is much easier to do the conversion from the JS world to LiveScript, and viceversa.

Introducing Laziness, pureness and static typing into the JS world is a much bigger challenge. I'd love to see some of these efforts take off; especially Elm, which is even more ambitious, as it not only provides a safer alternative to JS, but also to the DOM model and HTML altogether.

The biggest problem i see these projects facing is the abstraction gap. As the abstraction over JS/DOM that they provide is much bigger than, say, CoffeeScript of LiveScript, when that abstraction breaks and you have to dig into the generated JS/DOM world, it's very painful. And this is a necessary pain every time things don't work as expected and you need to debug in the browser. I think that for these projects to be successful efforts like source maps are crucially important. But for projects as ambitious as Fay or Elm, i think we need even better debugging tools; some environment where we can debug entirely within the abstraction layer that these languages provide, and make the cases where you have to resort back to JS much more uncommon.