ClojureScript, Lisp's Revenge [video]
I really like Clojure (and have enjoyed David Nolen's CLJS tutorials and guides), but I find ClojureScript to have terribly arcane tooling. Despite being familiar with Clojure, it's still 10 minutes of cargo-culting and copy-pasting before I can start actually working on a ClojureScript project. Slightly ironic for a language which places such an emphasis on removing "incidental complexity."