[gcv]

I think Ron was referring to the development process, rather than the finished program. The way Lisp languages and environments handle REPL-based interactive development is significantly more powerful and flexible than e.g., Rubython or even Haskell.

Modifying a running program to make a change as you develop it is an incredible speedup, relative to (recompiling and) restarting all the time, and even relative to reloading whole changed files.