We just got home & were amazed by the crowds. We must have been in the right places at the right time.

We went to MK, then Epcot on the 30th. We showed up for the Christmas parade at MK about 15 minutes before it started. There was a row of people sitting on the curb, then we were standing behind. At the last minute, a family came in & jumped in front of us, but we were still only 3 rows deep at the end of the parade. We didn't try to ride any rides at either park, but the crowd was also very manageable in Epcot, when we went for dinner that night. We only waited about 5 min. past our ADR at Le Bistro.
On NYE, we had dinner at HBD @ 5:50. After dinner, we walked onto TGMR. Star Tours had a 20 min. standby line, if we'd chosen to wait. We then saw Osborne Lights moving through easily, & headed to Epcot. Epcot WS was a madhouse. DHS crowds were nothing like that. We wished we'd stayed there. After wandering through WS, we went to FW where most of the rides, except TT & Soarin' were a 10 min. or less wait. I don't remember about Soarin, but TT was 50 min. SB. Strangely, people were camping out in the grass in FW to watch Illuminations. The sign said that area opened at 5 pm for viewing. I can't imagine how good they could see from there, especially to have waited so long. Leaving Epcot was a total nightmare. Many of the roads were blocked off in one direction causing our bus ride to take an hr. & 10 min. to get us back to the hotel. Cop cars were blocking entire lanes.
Today @ MK was great! We arrived at about 1:15pm. By our ADR time at 5:20pm, we had ridden standby on HM, PotC, Buzz, SW, IASW, Philharmagic & rode Peter Pan via FP. We even had to stand around & wait for our FP time to ride, then head to dinner. The lines were shorter than I've seen them in summer most of the time. The only ride we considered, but passed, was Pooh. The SB line was 50 min. & we decided not to bother getting a FP. We didn't stand in line longer than 25 min. for anything. Some of the lines said the wait was longer, i.e. Buzz said 35 min., but the actual wait time was only 13 min. We didn't check any of the other rides to see what the wait times were.
Apparently, the nightmare crowds left by the 30th. It was nothing like I feared. Admittedly, we didn't try many rides on the 30th & 31st, so I don't know what the lines were like other than the ones I mentioned. We've decided we'll probably go this year at the same time. We'll just avoid Epcot WS on NYE.