This had quickly become one of my favourite languages. If you see it from the point of view of expressiveness, it is really close to Python. It is quite new in the world of programming languages, but it is mature enough to be used by big players such as Twitter and Foursquare.
What i like of that language is mainly conciseness united with the possibility of using almost every tool and library from the Java world. It is a big plus indeed, and just that alone it gives many more tools than PHP, Python and so on.
Secondly, i really like the functional approach. I am not going to say it is better than imperative, it is just a different way to approach the same problem. It is a bit more difficult to follow at the beginning, but it offers many advantages, you don’t specify each step for instance but rather a group of transformations. I don’t want to get into detail, i am not a functional programming expert.
Last thing i want to mention is speed. Being compiled to Java Bytecode, it’s blazing fast… comparable with C or Java.
I did not mention it’s fun to use! here in London the user group started regular meetings 6-7 months ago and there is still that feeling of being a pioneer which is quite nice.