Why it matters
Cursive Clojure uses static analysis to provide some nice features that are hard to come by in Clojure editors, including underlining errors. Also, since it is built into IntelliJ, it handles projects (including projects with some Java classes) seamlessly. I have heard more than one person mention that they prefer it to Emacs after using Emacs for years.
About Colin Fleming
You can install Cursive Clojure by following this User Guide.