Just to report, I finally made it through on the phone, and the poor guy sounded like he was in the midst of running a marathon! He was VERY apologetic for the wait times and at having to put me further on hold.

In the end, he was able to restore me to E+ seating for all flights I'd previously been assigned to E+ (there was one flight on CO metal that UA couldn't previously put me up front). For that flight, he said I can get into E+ at check-in, so no big deal.

I'd also like to shoot Shannon a HUGE thank you for all the energy he's put into keeping us informed before, during and after the migration. He's been a tremendous help!