This trim really took in all the right ways.
The 'ghost' villages/pyramids are still carried over from previous worlds, which are just great fun to stumble across, and
I just went out to the Nether trim wall where I knew a previous fortress was, and it's moved over too! Actually it intersected with a new fortress, and the new one doesn't have any of the wonkiness of the last trim (missing spawners, etc). So that's great.
The End trim looks to be working as well. Even in previously explored areas new Cities are popping up, though I haven't been in there long enough to discover if any old ones carried over. I doubt it... they'd just be floating in space between islands.
Also, speaking of previously explored areas, we found llamas in a wiped area that was heavily explored. That didn't happen the last time with polar bears (they only spawned in previously unexplored areas), so maybe the new seed fixed all that.
MAJOR UPDATE: I no longer get set on fire exiting the CommEx portal. Best. Upgrade. Ever.