On OUr trip 1/12-1/17, we did the EMH at Epcot and at AK. The one at Epcot was from 9-midnight. The crowds emptied out very quickly. We did HISTA and the theater was only about 1/2 full. We tried to do Energy Adventure, but it was broken. We repeatedly rode Test Track. The last hour, we didn't even have to get off--just unbuckled and rebuckle the seats. I thought it was great.
We also did AK for part of one evening--open til 8 on Sunday night, which is not its ususal day. The crowds were great. On primevil whirl, they only had one side open. It was a longer wait earlier in the evening. Dinosaur was basically a walk-through. I was surprised by how light the crowds were as we left MK to go to AK because MK was a mess of people.
Unfortunately, because of timing, I wasn't able to hit the MGM or MK EMH, but I liked what I experienced.