"**It works like Java**. It's not "weird" like Clojure or Scala (and let's face it, they're both pretty weird.) You can learn it quickly. It was obviously designed to be accessible to Java developers.

**It's safer than Java**. It provides built-in support for many things that are handled in Java these days with annotation processors -- override checking, nullability analysis, etc. It also has safer numeric conversion rules, and although I'm not sure I like them, I have to appreciate how they force me to think about all my number representations.

**It's interoperable with Java**. And I mean their interop is flawless. I've seen too many JVM languages go down in flames because you couldn't subclass, I dunno, a static inner class of a nonstatic inner class, or whatever weird-ass edge case you needed at the time. Kotlin has made Java interop a top priority, which means migration to Kotlin can be done incrementally, one file at a time.

**It's succinct**. I'm a bit of a golfer, I'll be honest. All else being equal, I like shorter programs that do the same thing, if they're clear enough. Kotlin makes for a great round of golf. On average I find it to be about 5-10% shorter than the equivalent Jython code (which is sort of my gold standard), while remaining more readable and far more typesafe.

**It's practical**. Kotlin allows multiple classes per file, top-level functions, operator overloading, extension methods, type aliasing, string templating, and a whole bunch of other bog-standard language features that for whatever reason Java just never adopted even though everyone wanted them.

**It's evolving fast**. For instance they just launched coroutine support, which is going to provide the foundation for async/await, generators and all your other favorite non-threaded concurrency features.

**It's unashamed**. Kotlin often borrows great ideas from other languages, and doesn't try to hide it. They'll say, "We liked C#'s generics, so we did it that way." I like that.

**It's got DSLs**. No DSL should ever be created without serious consideration of the alternatives -- but a DSL done well can be a powerful tool. Look at Gradle's DSL, for instance, in comparison to the thousands of lines of XML in a typical Maven project. Kotlin makes that kind of thing easy.

**It's got one hell of an IDE**. Lately I've taken to writing new files in Emacs, which lets me bust out a ton of code very quickly, code which just happens to be full of horrible errors. And then I open it in IntelliJ and hit Alt-Enter like 50 times while the IDE fixes everything for me. It's a great symbiosis.

**It's fun**. Kotlin is just plain fun. Maybe it's subliminal advertising, since their keyword for declaring methods is fun. But it's somehow turned me from a surly professional programmer into a hobbyist again."