I've been in enough code reviews of Scala that did simple things like string processing that inevitably got sidetracked into a navel gazing discussion about type theory, pattern matching, and functional programming to not go near the language again anytime soon. You simply couldn't understand the code without understanding tons of incidental complexity about the language.

The Clojure community has its navel gazing of course, but every time I've been exposed to some crazy idea in that community it was always through the lens of providing real leverage for real problems. Most of the time when I've dealt with people trying to explain concepts to me for Scala code, I've walked away wondering what the point of it all was (beyond the fun Computer Science.)