Kotlin support on Android:
i never liked Java, not because of the language but for the usual bad design implementations and Android is one of those.
Then Kotlin arrived, it looked very promising but it's when i looked at Coroutines that it simply blew my mind:
you just have to write your code and the Kotlin's compliler "magic" will do most of the boring/complex stuff for you and it's even great performance wise!
I even refactored inter-process calls to simple sync functions with few like of code and for a non-android developer like me it's just love at first sight!