I like how the post focuses on the practical aspects of using Lisp first. I'm just a novice autodidact when it comes to Lisp, but the thing I absolutely love when learning or playing with the language is the interactive top level. I use SLIME on emacs when playing with Lisp at home. It reminds me a lot of the interactive top level available with most good RDBMS manager apps for use by DBA's and developers (TOAD, SQL Navigator, etc). It makes the work go by quickly and you manage to accomplish a lot. In contrast, when at work developing mostly Java web apps, web services, and stand-alone apps, progress comes seemingly much more slowly.
I must admit, I would have really liked to have seen the John McCarthy ask the question.