I would have thought cs50 is a cs0 course, and cs51 is the cs1. cs50 is the concentrators-and-non-concentrators course that's all flash and fun. What do you think is the cs0 at Harvard?

As for your point about Penn's CS120, I guess I don't fully understand the criterion. From the way you described it, CS120 seems like a CS1 course: not for someone who has had zero programming, but the very first course taken by most CS concentrators.

FWIW, I spoke to Benjamin Pierce about the structure of the course, and he said he didn't want to use "Real World OCaml" because it's too early of a course: he has students who he thinks don't yet understand things like what a scope is. From the sense I got from him, it's quite early in the curriculum.

That said, this is mostly minor quibbling. I think there's little doubt that "very early" courses, for some reasonable definition of "very early", lean towards Python. And reasonably so.