Hello. I've been watching Kotlin development for a long time and at this moment I really think it is the best static-typed programming language on top of jvm. One factor that stops me from investing more time in using it is that it is still has 'in development' status and the time it will be 'production ready' is unknown. This is connected with several bad thoughts, such as: 1. What if the language will be 'prod ready' only in 2-3 years? Whole ecosystem can change till that time, Kotlin grammar can change, standard libraries API can change, incompatibility might appear, etc. 2. In 2014 Java 8 will be released. Even right now it is hard to change java for something else (excellent IDE support, lingua franca for most of JVM devs, existing frameworks compatibility, confidence in future), but after java 8 it will be even harder - some of the features (lambda + compatible with it collections api) will appear in java. It means that even if someone have the urge to get some convenient functional programming features in language (lambdas + collection's api), this urge will be somewhat satisfied with Java 8. Scala has already gained significant (for alternative language) momentum for advanced developers (moreover, Scala has growing number of developers thanks to EPFL students), java will become less crippled safe bet, and Kotlin won't have a niche. If it will happen, it will be more safe to stay with Java and Scala because of the confidence in their future support.
To summarize, I think it is necessary to announce the date of the final release and to start polishing compiler, existing features, tools, make usable plugin for eclipse (personally - hate this IDE, but there are many who finds something adorable in it).