I still remember how, when learning common lisp, I kept looking for how to enable a breakpoint in my code. I wanted a conditional breakpoint that would fire under specific conditions. I was really surprised to learn that you just modify your code and insert a (when something (break)) -- and that (break) function call lands you in a debugger.

I found the elegance and convenience very impressive.

Clojure, unfortunately, is hard to debug, no matter how many trace macros one uses. In a long-running application I would much rather land in a debugger, inspect locals, think about what to do next, walk the frames on the stack, etc.