A modern lisp, with efficient, persistent data structures, targeting the jvm.
Pro Simplicity as a pillar of culture.
Simplicity is one of the pillars on which Clojure is built. Clojure tries to solve many problems in software development as simply as possible. Instead of building complex interfaces, objects or factories, it uses immutability and simple data structures.
Pro Designed for concurrency
Since Clojure is designed for concurrency, it offers things like Software Transaction Memory, functional programming without side-effects and immutable data structures right out of the box. This means that the development team can focus their energies on developing features instead of concurrency details.
Pro There are only the 11 basic instructions to learn
If you ignore the existence of a function, you can always recreate it using the 11 special forms. Later, if something you happen to do often appears to seem particularly handy, chances are that there is a built-in function for that. But you don't need to know or learn it upfront.
Con Very different semantics from mainstream programming languages