Good interview with Zach - I didn't realize that he lived in Maine.
I have mostly switched my Lisp development from Common Lisp to Clojure because that is what a customer wanted and now I am hooked on Clojure, but when do I use Common Lisp Zach's Quicklisp package management and installation system is very nice to use - I wish he had written it many years ago. In case you haven't tried Quicklisp yet: http://www.quicklisp.org/
BTW, if you work on OS X, and you want to get a good "IDE like" Common Lisp environment setup quickly, just install Clozure Common Lisp from Apple's AppStore (free), install Quicklisp, and set an alias like:
alias ClozureCL='/Applications/Clozure\ CL.app/Contents/MacOS/dx86cl64 &'
so you can quickly start the IDE in any directory.
I have mostly switched my Lisp development from Common Lisp to Clojure because that is what a customer wanted and now I am hooked on Clojure, but when do I use Common Lisp Zach's Quicklisp package management and installation system is very nice to use - I wish he had written it many years ago. In case you haven't tried Quicklisp yet: http://www.quicklisp.org/