That said, it's very much a cool hack, and worth doing on that basis alone.
Unfortunately I think JS is having a lot of responsibility heaped on its slightly creaky shoulders these days, due to the growth in mobile intarwebsing and every man and his dog looking for a quick way to build the app that is going to bring them fame and fortune. As a result of this, we're seeing a lot of these frameworks which compile [arguably!] 'better' fuller-featured languages down into JS.
Personally I'd rather a scenario where people could code in <insert language of choice> and embed this in HTML as easily and ubiquitously as JS can be embedded. A bit of a pipe-dream I know, but wouldn't it be great if we could exploit the cross-platform accessibility of web apps, without having to turn everyone into a Javascript hacker?
That would indeed be amazing. Anyone want to build it? :P
In fact the dom is defined in an IDL which can generate the dom API not only in javascript but a lot of other languages (Java/C++/etc)
This is an argument that tries to emotionally justify the limitations of web browsers that force us to compile down alternative languages into web "assembly".