I don't think it's so much that it's hard to get a productive working environment. In my experience, getting vim-fireplace working with a new Leiningen project takes nearly zero effort. Moreover, I get all sorts of nice functionality (easy evaluation of expressions, sourc/doc lookup, etc.). Getting all of these features with ClojureScript takes quite a bit more effort, especially connecting it all to a browser REPL. At least, this has been my experience.