As far as functional languages go, it's a nice compromise between the absolute purity of something like Haskell and the day-to-day practicalities necessitated by building practical, scalable things quickly (core.async, nice Java integration, runs on the JVM).

As far as looking like a parenthesis layer cake, that's part of the Lisp "tradition", really. One can look at is as the price you pay for true homoiconicity and powerful macros.