Mm. I had to do ML at uni. It's pretty much evil to it's core, I decided. And whenever you want to do something good, you just call a C library anyway...
I wouldn't want to try to achieve anything major using it. Could be quite useful for calling from imperative code for doing stuff like stream processing though.
Rendle and Haskell, sitting in a tree, R-E-C-U-R-S-I-N-G! :O
Too many languages, too little time.