@yole: after trying Kotlin some time ago and then coding in Java for couple of months and now getting back to Kotlin again i have to say that IDE support could be better. I don't have any specific issue except that sometimes IDE doesn't tell me that I have an error in my code and it won't compile. It may be connected with kapt actually but I and my coworkers have experienced this many times. And all I can do in this case is to manually go file after file and find code that is for example misspelled or something. In general I don't feel as comfortable and safe as when I code in Java. But I see that it's getting better and better so I hope we'll get there :)