Turns out the issue with the PS3 refusing 50Hz isn't QUITE as bad as I'd thought... though it's still far from ideal. The issue is not that the PS3 is searching for 50Hz material, merely that while it used to skip such signals, it now shuts the system down.
So why is this a problem on THE DESCENT? Countries still built on the PAL legacy of 50Hz tend to create materials like copyright warnings, studio logos, and menus at 50Hz, and that's exactly what Insomnia did for The Descent. While on PS3 firmware 2.6x, the system would encounter 50Hz material and then skip it in favor of going to the top menu. On 2.7x, when the PS3 encounters 50Hz it simply shuts the disc down. Hardly an ideal situation, and a real pain in the arse for anyone who's already (or planned to) import a region-free disc from a country that still has 50Hz power, which includes pretty much all of Europe, Africa, Australia, and roughly half of Asia and South America. From now on importing for the PS3 will be a total crapshot, with zero guarantee that the disc will even boot up... if you can get to the main menu, odds are you'll be fine.
Netflix still had hundreds of BD titles I can rent, and there's still plenty of movies I'll be buying locally, and - occasionally - from Hong Kong and Japan, which thankfully are still based on 60Hz power systems. Alternately, I'm already looking for more info on a Momo region-free player, which sounds like it would be the all-around perfect solution for non-US titles. Likely not quite as high a quality on the deinterlacing/scaling options as an Oppo, no, but better than the current nothing for import Blu-ray that I have going on at the moment. Oppo's BD player isn't region free, not even for DVD, so it's worthless as far as I'm concerned.