I use all three, depending on the task. Haskell is compiled and relatively speedy, as well as being great for writing custom parsers (plus in a lot of situations it parallelizes very easily). One thing I find Haskell to be really useful for is coercing large unstructured datasets into a format that is easier to feed into Python.

For instance, I once had to write a parser for the data coming off of a digitizer being fed by a rather complicated radiation detector array. It's in an obscure and somewhat bizarre binary format that is pretty tedious to work with because it involves a lot of state in the parser, plus the files are pretty enormous (they describe every radioactive particle hitting every detector in the array over several hours of measurement). My colleague wrote a horribly tedious script in Python to parse it that was complicated and agonizingly slow, but I was able to write a very natural 80-line Haskell program in a few hours that was several orders of magnitude faster as well as much more robust. I was just massaging the data to feed into Python, but it was far far easier to do in Haskell.

So I find for some tasks I want to reach for Haskell, because it's natural to express the solution in Haskell. Other stuff I wouldn't even consider it, especially for stuff like data processing and plotting Haskell is not as elegant. Right tool for the job and all.