Totally valid point. One of my housemates loves Haskell for very much the same reasons, and all other things being equal I'd prefer that as well (who wouldn't?)

Totally valid point. One of my housemates loves Haskell for very much the same reasons, and all other things being equal I'd prefer that as well (who wouldn't?). But of course, anyone who's worked on production systems knows that all the mathematical ideals in the world doesn't stop bugfixes from becoming a giant hairy mess. It's more your culture, skill, and process that allow or prevent that from getting refactored into a better solution and how long that takes. Any language can be a part of a clean or messy codebase, although some tend to skew towards one side or another - but I'd wager that's as much a factor of barrier to entry as anything else.