[davexunit]

But you always have to make some serious trade-offs. Sure, maybe you can use map and friends, but you usually don't get the nice things like tail-call recursion semantics (though Clojure doesn't have that either), efficient persistent data structures, proper first-class functions (looking at you, Ruby), lexical scope, etc.

I program in a functional style in all of the languages that I get paid to use, but I'm always sad about the lack of many useful features.