Indeed it's not the same language. I wasn't bit by the macro differences (which are probably the largest non-interop difference) since I tend not to use macros in my Clojure or ClojureScript code. Macros are going to be different since the macro compile host (JVM) is different than the run host (Javascript VM).

Other than macros and the VM interop (ugh I think (.-length str) is an eye-sore for property acesss), the core of the language is close enough that I Don't think of it 90% of the time.