So, I stopped into a semi-local thrift shop, as I'm occasionally wont to do. Their appliance room, as usual, had a whole wall of vacuums. They looked like a sad bunch, as usual - the obligatory bagless Bissels, old Dirt Devils, Hoovers that would be good but were in horrible states of disrepair, etc. I nearly walked away in annoyance when I chanced to spy the base of what had to be some kind of Tacony upright.
On closer inspection, it was a Simplicity 6970, and other than a dirty bag compartment and an odor like a wet dog that smokes, it looked fine - and was priced at $10! There was a beat-up Eureka Boss there too, with a VG2 brush roll.
I took them aside and tested - the Eureka had something horribly wrong with it. The motor was noisy as heck and sounded very wrong. I think it had a damaged fan and bad bearings and a snapped belt, it could barely pick up surface cruft and sounded extremely rough. I left that - too much trouble for forty bucks. The Simplicity, however, ran quite well, though the brush roll wasn't turning. When I popped off the sole plate, the reason was clear: broken belt. Real easy.
Stopped by the local vacuum shop on the way home, got some actual, real-deal Tacony HEPA bags (instead of the bojack crap that was in it) and a new belt, then cleaned the machine up with my trusty Filter Queen, and tested it out. While the suction and airflow don't seem quite as good as the FQ, the agitation is fantastic. It grooms the carpet much better and seemed to remove a lot of ground-in sandy stuff that the FQ takes quite a few passes to get. Color me impressed, overall. Certainly can't be beat for $10. Also a clear signal that I need a better power nozzle for the Filter Queen!