What really sets Haskell apart is the effort it goes to in its design to enforce functional programming. You can program in a functional style in pretty much any language, but it's all too easy to abandon at the first convenience. Haskell does not allow you to abandon functional programming, so you must take it to its logical conclusion, which is a final program that is easier to reason about, and sidesteps a whole class of the thorniest types of bugs.
When it comes to writing a program for real world use, you may find Haskell lacking in some practical fashion, but your final solution will be better for having known Haskell to begin with. I'm definitely not there yet, but so far learning Haskell has been much more enlightening than say, Lisp was in college.
