Intellij's La Clojure does a little more than syntax highlight: minimal refactoring support, rainbow parenthesis, smart parenthesis, syntax highlighted repl, great autocomplete support, awesome code navigation, autocomplete for java classes and live templates.
Not to mention that slurp forwards (Edit->Clojure->Slurp Forwards) is really nice. Example. Place your carret on |
(println|) (reduce + [1 2 3])
(println (reduce + [1 2 3]))