The biggest problem with FP being[1] code that only IEx will render as expected. As a teaching tool, my complaint would be that it abstracts so much of what it's doing that I question how much you're really learning. Everything I've ever learned in a Microsoft IDE was only useful in that IDE.
[1] Take this with a grain of salt, as I haven't used it in a while. But based on Microsoft's history, I'm still pretty confident saying it.