>> Scala is difficult for Java developers to learn, because Scala has new concepts in it, like type-classes or monads and these concepts are exposed within a static type system. Are these concepts useful? After using Scala for the last 2 years, I can bet my life on it. However there's a learning curve involved and Scala is definitely more expensive to learn than Java. That's why context matters. If a company has the resources to invest in this learning curve, then it's worth it, otherwise it isn't.
This sounds similar to some of the stories about Twitter's switch to Scala. The developers who liked Ruby loved Scala, while the rest of the team stuck with Java, I believe.
Or, instead of telling me that it's a free country, you could be productive, correct me and (ideally) provide a source. I'm happy to learn something new or have a mistaken belief corrected.
This sounds similar to some of the stories about Twitter's switch to Scala. The developers who liked Ruby loved Scala, while the rest of the team stuck with Java, I believe.