> but the longer your repl session is open and the more you change and compile, the more likely you are going to end up with a mixed state in memory that does not reflect how your program would behave if run from scratch.

I've seen this happen multiple times including during live Clojure talks at conferences. I also never found REPL driven development all that beneficial outside of quickly toying with trivial pure functions and that's possible in basically every popular language these days.