Cutting the nr of LOC in half, while at the same time getting even more type safety, seems like a pretty big win for any Java project, Android or not.

May I ask why? Is it because Kotlin doesn't bring much new to the table besides fixing a few minor annoyances with Java? I have the same feeling, but can't put my finger on why exactly Kotlin seems unnecessary, except that it's a modern language that doesn't have union types.