I think what GP is complaining about is the compilation step, which requires a JVM and isn't exactly the fastest.
Touche - You don't need project.clj and leiningen and can run a command basically like you're asking for. I'm not sure how much faster it is than using leiningen and cljsbuild, as I haven't tried it: https://github.com/clojure/clojurescript/wiki/Quick-Start#cl...