Yes. I lead a team that's writing a new piece of what can be thought of as enterprise middleware in Kotlin:

https://github.com/corda/corda

It's a distributed ledger/blockchain system being written for large, conservative banks and is around ~90%+ Kotlin code.

There's not much to say about it, it works fine, I wrote about it here:

https://www.reddit.com/r/programming/comments/6bqo7n/kotlin_...