Check out type-driven development (there’s some good F# example blogs) - honestly it’s like TDD on steroids. Having no type system scares me now, having worked in a Python startup before moving to a Haskell shop and seeing the difference in development quality (speed is surprisingly similar too).
I think we are on the same page. I also write Haskell for food. What I'm saying is that if you write Haskell professionally and types slow you down, ie. you always try to come up with the best possible abstraction for everything, then that's a problem. It should do the opposite: give you wings while prototyping, iterating fast and refactoring(!!) as well as great comfort knowing that you have all its amazingly powerful tools in your arsenal if and when you need them.
