It's a refresher in just how powerful Lisp is. For a language approaching 50 years old, it's pretty amazing.

I always crack up a little when I think about the reasons Lisp and Smalltalk couldn't go "mainstream" - why, they use too many resources! (My web browser looks like it's running in 41 meg so I can type into a non-styled text box. I doubt Lisp or Smalltalk would do worse than that:)

Anyway, if you've never studied Lisp, these lectuers are a good excuse for trying it out.