[beggi]

I haven't tried Scala but since no one has mentioned it: Clojure is a pleasure to work with if you want a functional language in JVM.

I have no idea which and how many startups use Clojure, besides Datomic :) It would be interesting to know.

[dwelch2344]

I'd like to agree here. IMO up-and-coming Clojure is an up-and-coming competitor to Scala. As a Lisp variant for the JVM, I'm a major fan of it.

Unfortunately I can't share any personal experience as the core of my work is in the Enterprise so I haven't had the right opportunity to present itself. But if you're coming from a mathematical background you should check it out