I really would like to use haskell (ghc) even more but the lack of 64 support on windows is a realworld troublemaker. When your doing anything with large dataset you must constantly think about what will happen when lazyness and garbage collector kicks you in the face because you hit the classic win32 bit 2GB upper limit. Profiling and watch for spaceleaks will save you but you wouldn't even be doing this in a proper 64bits environment.
Ah, fwiw I haven't used Windows since 2007 so this wasn't on my radar, but I do hope they get that fixed. Or maybe the Haskell team is intentionally dragging their feet there, in order to "avoid success at all costs"...