Whilst undoubtedly cool, and based on super-interesting research, it's worth bearing in mind this is a compile-to-Racket language. Anyone who's used a compile-to-JS language will be familiar with the drawbacks of this approach.
Pretty much. Take the example in the post: the web server is Racket's web server with an FFI wrapper. So you're using an API that was never designed with Hackett's type system in mind. So now you've got the choice between exposing an efficient or an idiomatic interface. And so on...
