Some of his comparisons are true -- Haskell is relatively hard to comprehend for programmers who are used to imperative languages, but Haskell is imo the best language for learning functional programming techniques. The core of the language is beautiful and pretty simple. Intermediate concepts like monads are more difficult because you can look at them in more than one way and they take some time to really understand. While learning those concepts it also becomes clear why other language designers have made different choices. And that is imo the best part of learning Haskell. After that learning mixed languages like F# and Scala is easy.