The great thing about the whole Apple ][ system was that it was sophisticated enough to actually do stuff but simple enough that a single person could understand it (largely because it was mostly the work of a single person). To this day, my mental model of how a computer works is the Apple ][.
Indeed. I have often wondered why university courses tend to use their own made-up machines to teach this stuff, as opposed to using the Apple II (or some of its near-contemporaries).