@yole: the main reason to use kotlin is to improve your own productivity, but instead of getting any productivity boost, android developers are facing multiple kotlin issues, like:
1. Incompatibilities between Android Studio and Kotlin plugin
2. Incompatibilities between android gradle plugin and kotlin gradle plugin
3. Multiple kapt issues
4. Incremental compilation issues that make it completely unusable
5. Slow compilation
6. Databinding issues, here is the most frustrating one
https://youtrack.jetbrains.com/issue/KT-12402