The functional programming aspect of Clojure reminds me of OCaml. In my first computer science class they had us do OCaml before Java, and I remember recursion was a huge topic, and it looks like Clojure allows us to do the kind of efficient recursion we need for sorting algorithms, mathematical programming and the like. I personally haven't see Clojure until today, and it looks like something I will pick up again considering how useful I think functional programming is.
A lot of people are using Clojure because of its functional programming style; coupled with the fact that all of Clojure's core data-structures are immutable, and it has a very efficient implementation of STM (software transactional memory) that allows for (correct!) lock-less multi-threaded programming. This is fantastic news for multi-core processors (all modern hardware have multiple cores, and this trend will keep going).
In short, Clojure's functional paradigm and concurrency support is itself a huge win. Couple that with the fact that it runs on the JVM, and that it is a modern LISP, it is no surprise that it is seeing remarkable adoption across many domains.