In college I was required to take a course using SML (which has a type system that is sort of like Haskell's I think; Haskell's may have been based on it). I was not all that academically driven that semester, and I was kind of taken by surprise by how hard the language was, once I started doing the later projects, and I barely got through the course. That was my only exposure to functional programming until after college, when I wanted to make up for that and I undertook to learn Scheme. I didn't have much trouble with Scheme, and the functional concepts I'd heard about in the course finally made sense. If you're trying to learn the functional style, I don't see the point in learning at the same time a complex type system. The type system isn't a natural consequence of functional programming, it's something that's not really related but adds a lot of difficulty.

I don't want to start a flame war, but I view types as being sort of peripheral to the task of getting the computer to do things. If type systems are getting in the way of programming, priorities are getting mixed up.