I learned Clojure with Joy of Clojure, the early access version, coming from a Python background with very little practical experience in Java or Lisp. It's an excellent book.

The biggest advantage for my coding has actually been in my day-to-day Python work, where I'm much improved at designing functionally, parallelizing with multiprocessing, and building decorators and context functions to remove boilerplate code. So my Python is faster and cleaner; this is all thanks to being able to to think better about code design after working in Clojure.

For a good example of "why Clojure" take a look at Cascalog:

https://www.assembla.com/wiki/show/d9Z8_q-Omr35zteJe5cbLr

which leverages Hadoop/Cascading Java libraries and combines them with a Lisp-style custom query language.