Today's Update:
It is not the transmission. The Service Advisor called me about an hour after they took the Escape back for diagnostic checks. She asked if I could come in and go on a test drive with the tech, because he couldn't replicate the issue(s). About ten minutes later, we were pulling out of the dealership, and I immediately told him that we needed to hit the highway. He had driven it around in the city, but couldn't get the issues to surface,
Once on the on ramp, I told him to get it to at least 40 mph, then moderately accelerate. He did so, and the vibrations were so bad, I could feel them in the floorboards on the passenger side ... he did this a few times, and each time was "rewarded" with the vibrations. I then told him while we were on a moderate incline to accelerate the same way. The Gremlins showed themselves again, and he said he is now having doubts that the transmission is the issue, as the RPMs were steady throughout the drive.
Fast-forward a few hours, and the Service Advisor called me back. Turns out that both rear trailing arms, the LF driveshaft, a few tie rod ends and some other misc suspension pieces were bad. Parts won't be in until next week, but the car is safe to drive until they arrive.
The best news? Everything that is at issue IS covered by the extended warranty, so all we owe is the $100 deductable, plus they removed the factory junk lug nuts and replaced them with my Summit Racing lug nuts, free of charge!