I used Scala for one company I founded and the Python Paradox to be true. People who already knew Scala were generally much more accomplished programmers and for the people who didn't know, the learning of it was a great test of their ability. Here's why: as a hiring manager, I know it's possible to learn Scala. So if someone couldn't learn it and be productive within 30 days I knew they weren't sharp. (FYI, everyone did learn it quickly, but frankly, the best programmers can learn a new language in a weekend.)