A primary benefit of things like Wisp is it makes it easier for non-clojure users to dive in and learn a clojurescript like language. I like JS and I like Lisps but the learning curve for clojurescript is too much if you don't know Clojure already. Wisp feels much more JS like; with my decent JS and decent Scheme knowledge I feel I could just dive in and play with it. Clojurescript does not leave me with the same impression, it feels like a lot of work to get up and learning.

Clojurescript's heavy dependence on the Clojure environment (JVM, leinigren etc) make it a real pain to get setup for. I have looked into clojurescript several times but thought "I better master clojure first". I have been getting a hang of Clojure slowly and plan to tackle learning clojurescript eventually but something like Wisp opens up the possibility of diving in without needing to be comfortable with all the Java crap.

I only tend to take up something when it takes me five minutes to start learning. I think most are the same way; it's the reason why Codecademy is so popular and why clojurescript's primary user base is Clojure users. The more users that can start learning a language in five minutes the better it is for that language. Clojure beat out other Lisp implementations primarily because it was easier to dive into for a greater number of humans than any other Lisp.

Wisp and other implementations like it make diving into Lisp->js languages much easier. It removes the large roadblock that is Java, a roadblock that is unnecessary if your target language is JS not Java.