Steve Yegge says it's cool.
I first noticed Kotlin a year or two ago. I was doing some Java dev at home and thought "this sucks, I really wish I had C# features on the JVM". I ended up reading about Xtend (Eclipse world) and Kotlin (Intellij world). When confronted with a new library or language, my first question is always "will I be able to compile or upgrade this in 10 years' time?". Many of my pet projects at home have been kicking around for that long or longer, and I've no shortage of fun things I'd rather be doing than migrating old code.
So, will Kotlin take off? Compared to some of the possibly-the-next-big-thing languages I've looked at over the years, Kotlin seems... different. I can't say why I think that. The fact that Jetbrains is behind it might be the thing that makes the difference. Maybe.