pg mentioned that he uses vi with a REPL ( http://news.ycombinator.com/comments?id=587 ).
I recently began using emacs + SLIME for writing Lisp and revert back to vim for everything else. I've also tried vim + VIlisp.vim, which sends Lisp code to a running Lisp interpreter. It seemed pretty decent though I don't really have enough experience writing Lisp to really compare.
Anyone else write Lisp in vi?
SLIME is great, but I really miss vim sometimes. Fortunately, Slim-Vim is in the works by the author of VIlisp.vim. Here's a couple comment pages on Lisp with vi/emacs: