Hello there! I am concerned about unsigned types - I know that they are experimental yet, but I'd like to use them in production code. Should I worry about that they can be removed from language?

Hello @Nikita Yatskivskiy! I personally don't worry too much about that, but I stay cautious for public APIs. See this part of KotlinConf Keynote 2018 about language evolution principles for Kotlin:

There's text here: https://kotlinlang.org/docs/reference/basic-types.html#experimental-status-of-unsigned-integers In short, they don't guarantee any stability.