I don’t know much Clojure, but I thought that lack of TCO was not a problem because you can just manually add `recur` (http://clojure.org/special_forms#Special%20Forms--%28recur%2...) when you need it. Are there situations where `recur` doesn’t work but tail-call optimization would help?
In my talk I use a finite state machine as an example of something that can really benefit from proper tail calls. In this case, the difference between proper tail calls and loop/recur is the difference between "compiling" the FSM and running the FSM in an interpreter loop.