@PRR: I have a layman's understanding of the generic different ADC/DAC types, maybe just a little more than what can be gleaned from Wikipedia. While I was working on this I did look up what patent drawings I could find regarding folding flash ADCs but they were mostly for stuff that would be fabricated on a single slab of silicon, way out of my comfort zone. I'm not really surprised that this ground has been covered before, but I am pleased that I was able to discover it independently.
@Taylor: There are a couple things to watch out for when going from simulation to real parts with this build. First, if you use an op-amp it has to tolerate whatever differential voltages may appear at its inputs. For a small full-scale input range, this differential can be negligible. For a large full-scale input range, it might be better to use comparators that can handle such conditions gracefully.
Second, the simulation assumes the output can swing from zero to nine volts exactly. A rail-rail op-amp will be close enough but a general purpose one will at best swing to within a volt or two of the supplies. This makes the voltage at the resistive divider different so you get a deviation from the expected values; the result is some bits do not appear in the sequence. I'm still working on a way to calculate these values reliably. With rail-rail outputs it's just ratios, but with not-quite rail-rail outputs I think there might be actual math involved.
What I did was use DC input voltage that I could sweep manually (a pot across the rails), and LEDs on the op-amp outputs to monitor the binary output. Then I subbed resistor values until I got all the binary combinations. Now, I would start with the values in the sim and tweak with trimpots as needed.
@Quackzed:

@toneman: I may just have to buy a copy of that issue from PAIA, but I don't know which issue...
@all: thanks for the kind words.

I think there is a lot of potential in this thing as an audio mangler or noisemaker, but also as a way for folks to dabble with digital processing in a very raw and intimate way with discrete XOR/AND/OR chips as toneman suggested.