The biggest problem with Scala for me are very cryptic compilation errors with several line long type informations that do not match each other. The second pro

The biggest problem with Scala for me are very cryptic compilation errors with several line long type informations that do not match each other. The second problem is DDL hell. Too many changes to APIs, binary compatibility, dropped classes from 2.7.x -> 2.8.x -> 2.9.x. That said I'm very happy with Scala as a language, but they should fix those problems.