Reggie> There are several arguments for common lisp. Michael> I claim that migration to Common Lisp is roughly as Michael> expensive as migration to Scheme. But the theses was that Common Lisp is a better language for developing large software products with. So perhaps it "costs" the same to get to the point where you can start writing code in the new language, but one is better than the other for creating complex interworking systems. (For code developers, system administration, process control interfaces, ... (tell me what else! I'm interested.))