AFAIK(according to my FP teacher): a) Too complex compiler and lazy nature of haskell - generated code is hard to debug and optimise. Small changes to code might change how thing's gonna be executed so you lose control, where in OCaml it's quite straightforward and you can guess how generated code will look like. b) We had quite good intro at our university.

I like how succint haskell/ML syntax is. But I prefer practical work and controll so I personally plan to learn/use either F# or Reason/Ocaml.