Why would you have nil in a list of integers? In cases where you encounter nil instead of some type you look for you can add behavior to nil without doing if nil? in the function all the time.

I would agree that not having nil is better if you have these big typesystems but for a dynamic languge its hard to avoid.

Question: Don't these static langauge use "unit" to signal what nil would do in clojure (in some casses)?