Coming from CS and computational math background, I used mostly C++ for production and Python for prototyping and data analysis. I wanted to learn some new language for JVM, Clojure and Scala being the main (if not the only) contenders. I may learn Clojure anyway, but what tipped the scale to learning Scala first was wonderful Coursera course in functional programming by Martin Odersky, using Scala as a language, obviously.

A very short summary of my impressions from Scala: * It is beautiful, I felt the half-forgotten beauty of functional programming once again

* Scala worksheets (quick scratch to evaluate whole code snippets with immediate feedback) are awesome. I love them even more than REPL (Then again, I love IPython notebook more than Python REPL too)

* Scala seems a bit heavy in terms of number of concepts

* Scala can be terse and very expressive, but pretty verbose if you need it to be

* Compilation of large programs is slow and eats gobs of memory

* tail-call optimize everything