I was lucky enough to have a second hand Apple ][ from a "hacker", it had a ][+ rom and was pretty much loaded to the gills with a "z80 softcard" and etc. The slot 3 80-column card also had 16K RAM and was the only full-sized card in the machine. (It also came with full documentation if you wanted to burn a different font into a ROM.) So I had a 64K machine, but slot 0 was empty. Unfortunately I never had docs for Pascal, so I never bothered learning it and instead was mentally mutilated by BASIC.
A full-sized Apple card was a good bit less tall than a PC AT card and had to be angled to fit the case. e.g. [0]
I would think the 10MB Sider HD was a bigger deal. A friend of mine used one to run a BBS in Toronto back in the day. Before that, he had a custom setup that had a pair of 8" floppies, which was pretty uncommon for the Apple ][ platform.
A full-sized Apple card was a good bit less tall than a PC AT card and had to be angled to fit the case. e.g. [0]
[0] http://www.applelogic.org/files/AVOChires.jpg