The best part about using lein as opposed to maven or gradle build systems for java projects, is that once set up correctly its very easy to get started with any type of new library without having to worry too much! There are some things I would like to see in terms of functionality but overall this tool works really well and has helped me start many different types of web applications quickly and easily. Nothing at all so far! Great if you're looking to jump into clojure programming fast. We have been able to develop our own custom frameworks more efficiently than ever before which allows us quicker time-to market.