I've been trying to come up with a general way to rank Haskell experience, and so far I've got:

Beginner: Can read the basic syntax, knows about E.G. Monads and folds

Intermediate: Understands and can use the more advanced classes like Applicative, Arrow, lenses, and how to use things like fix

Advanced: ??? Makes new powerful classes/libraries like Pipe, Conduit, or Netwire? Can easily translate a problem domain into a concise and elegant type representation.

Maybe there needs to be some more layers in there, I don't know... also the advanced level feels weak to me. I'm still somewhere between beginner and intermediate myself.

Well I don't claim to understand the mathematical basis of Monads, and I don't use arrows and just started using applicative more often. Lenses rock and I have used those for a long time. I do build my own Monad Transformers so maybe I am still a beginning with intermediate tendencies. :-)