[metroholografix]

Common Lisp on Emacs via SLIME is not competitive with Smalltalk, re: "interactive experience" since Emacs is not the native substrate of CL, but essentially an out-of-process experience. If you want to experience CL at its best, you need to run Symbolics Genera.

Emacs with Emacs Lisp on the other hand offers a great interactive experience that also manages to easily surpass every modern Smalltalk incarnation in practicality and size of development community. So if running Genera isn't easily doable, this will give you a taste of what Lisp interactivity is all about.