Having studied Lisp and recently started on Haskell, I find Lisp to have a shallower learning curve. For Lisp, people fear the day they have to learn its macros. For Haskell, that monster lurking in the closet is the type system.
But you can be productive in (most) Lisp(s) without touching macros. It is often suggested to try very hard to do so. And I've personally found that, library spelling issues aside, Python code translates almost 1-to-1 to Lisp with simple text replacements.
But any non-trivial application in Haskell is going to have to approach problems in fairly different ways than any other language. Lazy evaluation; pure, side-effect-free functions; types and type classes and all that jazz; emphasis on solutions involving the "fold" function, rather than recursion. It's significantly different than most other languages I've encountered.
