That tutorial is deeply unimpressive. It seems very excited about APL having functions, and not directly mapping to machine-level constructs. In 1962 I can imagine that being impressive (if you weren't familiar with Lisp or ALGOL); today, not so much. The one thing that does seem somewhat interesting is the emphasis it puts on "operators" (i.e., second-order functions). This is obviously not new to anyone familiar with functional programming, but I do like the way that tutorial jumps in quite quickly to the practical utility of a few simple second-order functions (reduce, product, map).
Like I said, it's hard to find good ones; I didn't say I had succeeded. I learned a bit of it for a programming language design course, but I never got beyond the basic concepts.
