Java is deliberately not programmer-orientated. That's the point of using it — it was designed to restrict the kind of trouble programmers can get themselves into. If you're stuck with the JVM, I guess the question is: how much rope do you want to give your programmers? Scala is essentially the opposite answer to Java.

This was an interesting read but I disagree with this assertion. Java's lack of power as a language hasn't meant that people haven't written huge, complex, unmaintainable messes with it. Indeed, I think all the crazy dependency injection frameworks, configuration-by-XML, and other general insanity is due in part to the language's lack of power. Things that are simple in other languages (say, dependency injection, which can be replaced with runtime stubbing in Ruby or mixing in traits in Scala) often require painful and complicated ad-hoc solutions in Java.

That said, it is possible to write code in Scala that requires a PhD in category theory to understand (see Scalaz), but there are also many examples of simple, functional, easy to understand code (see stuff that has come out of Twitter, like Kestrel or Nagatti).

I think in practice, working with the modern Java ecosystem gives one at least as much rope to hang oneself as using Scala does.