I found the Michigan interview rather stressless actually. We were stressed that the environment was so relaxed. There was a short writing activity, but I'm sure it's mostly so they know you can write full paragraphs. As for the MMI, they were kind of fun and you get to meet more faculty and students. The only down part I can recall was the three hour presentations in the morning. We were running late, so there weren't really any breaks in between. Towards the end, all of us were squirming in our seats.