Paulo Vilella of Accenture added his views:

“For small to medium projects, I believe Scala is right now a great alternative to Java for higher productivity and agility, without compromising on performance and compatibility. For the large, complex business systems we typically build, I see Scala as an important adjunct to Java but not as a replacement (at least in the near term). I see great potential in the use of Scala for building selected portions of large Java applications, for example: high-productivity development of quality-critical complex business logic (statically-typed functional programming), high-performance concurrent processing (actors), architecture components and frameworks in general, domain-specific languages for application configuration/customization, and maybe even user interface development. Thus, a large project can significantly benefit from Scala with a relatively small number of Scala developers working in conjunction with a larger Java team.”