What I think it is slower right now are the tools. Sometimes IdeaJ stucks. I guess they will be improving the performance slowly as right now they are other things in the language more important to focus.
Re:Kotlin 1.1: What’s coming in the standard library
by vbezhenar on Wednesday January 25, 2017 @05:17AM
(#13480211)
Jetbrains uses Kotlin for their own projects, including Intellij Idea. So you can be sure, that its support will be reasonably good, they use it themselves after all.
What I think it is slower right now are the tools. Sometimes IdeaJ stucks. I guess they will be improving the performance slowly as right now they are other things in the language more important to focus.