I’m a big fan of the prefix notation. It makes everything appear the same (if-statements, function calls , etc). I like how it removes the need for operator precedence rules.
All the parentheses
Once you get into learning Clojure and you have written a small application, you don’t really see the parens anymore. Sure, sometimes you still get the Unbalanced parens error but those are easy to spot. If you are afraid of learning a LISP because of this, don’t worry, you’ll be fine.
Let’s just say that the start-up time of the JVM isn’t the fastest. This makes Clojure effectively useless for writing utility scripts. However, the JVM is a robust platform that runs your code really fast. With Clojure, you get all the benefits of the JVM: garbage collection, JIT, uberjars, etc. Using Java libraries in Clojure is usually pretty straightforward if you know the basics of Java (but the code isn’t the prettiest). This is great because some of the lower level stuff doesn’t have to be reimplemented (think SHA1 digests, sockets, etc).
The language itself seems to be documented pretty well. I haven’t had any issues when trying to find the signature for a built-in function. However, the community isn’t exactly known for writing documentation. Most of the time, you find a library on Github and you are left to read the source. If you are lucky, you are told what to import and a few basic examples. Good documentation is something I take for granted coming from the Python world.
While you can certainly find a lot of good libraries for doing common things, one area is still painful to develop for: the web. Clojure still needs a Django-like web framework that has all the batteries included. Right now, the only popular web framework is Noir and it’s more like Sinatra or Flask. Without a Django-like platform, you end up reinventing all the common things for every application: authentication, form validation, ORM, etc.
I really like the language. I like the functional aspects of it and the immutability. I like lazy sequences and refs. What I don’t like is that the community and the ecosystem is still a bit young and immature. I find myself waiting for stuff to happen before I can use this language more.