I haven't used Scala for application development (I'm talking about apps with a UI here). I really like it on the server -- easy to refactor, self documenting,

I haven't used Scala for application development (I'm talking about apps with a UI here). I really like it on the server -- easy to refactor, self documenting, great implicit typing so it feels like a "safer, faster" ruby or python. I'm just really happy with Scala. Highly recommended, and the Akka library (Erlang for Scala, essentially) is fantastic.