Although I am not sure about the premise - I doubt Haskell, as a language close to mathematics, can be learned fast. This tutorial seems quite shallow on some things, like monads.
I am not sure any definition does that justice. It's similar with concept of recursion - it's easy to define (function calls itself), but to put it into programming practice (writing all loops as recursion), that's a lot harder.
I read "Learn Yourself a Haskell" as a tutorial (which is in my opinion great) and still it was a lot of work to figure out this: http://blog.tmorris.net/posts/20-intermediate-haskell-exerci...
Then I started reading http://www.haskell.org/haskellwiki/All_About_Monads but didn't finish it yet (I was playing with Haskell, just figuring out how to structure the application). IMHO, unless you understand all that, how to put monad concept into practice, you don't really know monads.