Ranked in these QuestionsQuestion Ranking
Pro Immutability is the default
Clojure programmers are highly encouraged to use immutable data in their code. Therefore, most data will be immutable by default.
State change is handled by functions (for transformations) and atoms (an abstraction that encapsulates the idea of some entity having an identity).
Pro Minimal syntax
Being a LISP, programs are simple: they're just functions and data. That it doesn't get bogged down with syntax or the loftier FP concepts like monads makes it one of most approachable functional languages for beginners.
Pro Tries to solve problems as simply as possible
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 Good for writing concurrent programs
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 Huge ecosystem of libraries to work with
There's a very large ecosystem of high-quality Clojure libraries which developers can use. One example is Incanter. It's a great data analytics library and a very powerful tool for dealing with matrices, datasets and csv files.
Pro Rich Hickey
The creator is so awesome, he's a feature. Just look up his talks and see why.
Pro Cross platform
Clojure compiles to JVM bytecode and runs inside the JVM. This means that applications written in Clojure are cross-platform out of the box.
Pro Great tool used in automating, configuring and managing dependencies available
Clojure has an elegant macro system which enables language additions, Domain-specific languages (DSLs), to be created much easier than most other languages (with the exception of Racket, perhaps).
Pro Dynamic language
A superb data processing language. While rich type and specification systems are available they are optional.
Pro Game is available with which you can learn Clojure
Nightmod is a tool used to make "live-moddable" games. It displays the game's code while you are playing and allows you to inject new code using Clojure. This can be a fun and useful experience for people trying to learn Clojure.
Con Confusing error messages
Clojure's error messages more often than not are very confusing. They usually involve stack traces that do not thoroughly explain where the error was caused or what caused it.
Con Dynamic types
You can put anything in. This makes reasoning about code after a time has passed very hard.
Con Tied to the JVM and it's limitations.
Some language constructs were obviously created as workarounds for JVM limitations. This makes the language much less elegant than it could have been.
Also, the JVM has a very cumbersome FFI.
Con Syntax can be alien / jarring for those used to other Lisps
Perhaps some may consider this attribute an advantage, but I do not. Clojure does not attempt to maintain significant compatibility with other Lisps. So, if you already know a Lisp or are used to the way Lisp works in general, you'll probably be confused if you take a look at Clojure. See these resources for more details on this subject: