Excellent! I've started using Vert.x with Kotlin instead of PHP for making restful API's and it's wonderful. Event driven, strongly typed and performant. Looking forward to trying this out.
Did you find the documentation to be a bit painful? I gave it a shot for API endpoints too, and was very frustrated that Kotlin felt like a fourth class citizen... and the existing docs displayed one of my biggest pet peeves with most Java-esque docs; "we won't mention the imports, you'll probably have an IDE that figures those out magically". As a Vim user, that's a bit more difficult.