Follow up report: Kickass!
I was able to do some testing this weekend while the son was at his mom's place, and I am officially a fan. Between the 1w/10w/20w switch and the cab's built in attenuator dial, it looks like I can get most of the tones I want, regardless of volume. I've only tried a few pedals on it (Big Muff Pi Deluxe, Holy Grail Reverb, Soul Food & Zoom G3X), but it seems to take them well going into the front and in the effects loop.
I may, just for shits and grins, swap an Eminence Swamp Thang into the cab to see how it sounds (the speaker sounds good but still seems a little tightass; I'm sure it'll sound better with time).
The only "problem" is that the wattage selection switch on the "pushed" channel is miswired so that 10w=20 and 20w=10, but that's a very minor annoyance.