It is probably not a good sign that it can be immediately compared to every modern (and not so modern) language in existence.
I really like that it is incorporating good parts of many, more terse languages. Nothing wrong with selectively absorbing good ideas.
But a huge part is the interactive nature. I dabbled in Smalltalk some years ago and have been annoyed at compiled languages ever since, resorting to things like http://injectionforxcode.com to gain some of that back (on iOS).
Having a live environment can only be appreciated once it has been taken away. I think developing for Apple devices might just become one of the more programming pleasant experiences.