Recs.
Updated
Specs
Pros
Pro Max power possible
Using the macros system and the fact that the language is completely available in any stages of evaluating the code - reading, compiling and executing - you have access to every paradigm, every feature and every concept discovered so far in the software development. If something is missing, you can add it to the language and go on with your own problem.
Pro Image based runtime
The state of the program may be saved and reloaded as an image, supporting safer modification of the running program. New code may be compiled into the image as the program runs, while late binding ensures that symbol redefinitions take effect throughout the program.
Cons
Recommendations
Comments
Out of Date Pros + Cons
Con Obscure and non-obvious way to distribute completed software
Common Lisp was designed for systems where it (Common Lisp) is the Operating System. So its infrastructure misses usual facilities to make completely stand-alone programs, separate from the runtime installed in the base OS. Different implementations solve this problem in different ways.
Con Hard to use outdated infrastructure
Possibly the only kind of IDE you can get with Common Lisp is Emacs+Slime. Static code analysis, automated testing, code completion, code navigation - all inferior to mainstream languages.