Other than that I would agree with him though. Subtype polymorphism + runtime (single or multiple) dispatch.

Multiple dispatch is one of the things I really miss about Common Lisp. I do like OOP, but often the most intuitive way to think about something is multiple dispatch, and trying to shove it into a single dispatch model can produce some really ugly code. I'm pretty sure that is the main reason there are so many anti-OOP zealots in the world.

Also, I didn't realize Dylan had multiple dispatch. I should take a look at it sometime.