I never programmed in haskell, but I did in clojure and I must say that functional style and number crunching fit really nice. Said that, I am not sure you can beat things like numpy or pandas when it comes to complex/big datasets. I looked around in the haskell world and it seems that to do the same as, say, in pandas you need to write a lot of things yourself and you can't rely on the same superb documentation.

But I will be really happy to be proven wrong. I really think lots of things would be easier in Haskell.