clockworkant: my experience is pretty good so far, I was thinking to use either Kotlin or TypeScript because I wanted some type safety and real classes. I chose Kotlin because I was experienced with it, vs. not knowing anything about TypeScript - I haven't really come across any bugs so far, so I'd say it's stable ( just mentioning this because we now have Kotlin 1.1 and I read JS support prior to 1.1 was experimental) - the main problem regarding experimental status is that a lot of the code out there on the net, code examples and some libraries use deprecated language features... things you come across by googling... so just keep that in mind when you google