Part of Kotlin's pedigree are some ex-developers of Groovy, i.e. James Strachan (Groovy's creator) and Alex Tkachman (creator of Groovy++, the inspiration for G

Part of Kotlin's pedigree are some ex-developers of Groovy, i.e. James Strachan (Groovy's creator) and Alex Tkachman (creator of Groovy++, the inspiration for Groovy's static type-checking). They bring a deep knowledge of implementation pitfalls that can only be gained from doing it wrong the first time. Of course, Scala creator Martin Odersky completely rewrote Scala after version 1.0, and even in version 2.x, has considered fixing stuff between point releases to be more important than backwards compatibility, so Scala similarly ought to be quite polished by now (version 2.10), in both feature set and implementation.