Using a language that isn't already in every shop may limit hiring at first glance, but it will automatically select for folks who have an important sense of craft for the work they do and pay close attention to where there is a lack of return on investment in languages, platforms and applications. People who really care about FP will likely be easier to retain than those who use Blub and couldn't care less. Go is shiny right now. What will be shiny later? Lisp is not shiny but it is power like power has never known with Blub.

Aside: I've not found Clojure to be slower than Java and I've benched it. It is fast, fast, fast. As fast as Go even doing the concurrent thing: benched that too. I've even found that Clojure can edge out Java in many cases because of its inherent laziness: the fastest way to expedite a job is not to have to do it in the first place.