We went back in Sept of 2010, and I don't remember if I posted about it or not, but I will again.
We LOVE the train. My kids were in FL at a really nice resort and they all said they were looking forward to going home just to ride the train!
We have never done the bedrooms, but after looking at them, they felt too claustrphobic for me. In coach we have always been able to spread out and get separate seating for all of us. If we weren't able to do so, I might feel differntly.
On our way home, the ticket agent asked me how old my kids were, they were 15, 13 and 10, and he told us he would put us in the adult car. I was so glad he did! On the way back, the kid car was filled with little ones and they were very noisy, every time we had to cut through the car to get to the lounge/dining area. I don't know how it was at night, but even during the daylight hours, the noise would have bothered me; past that stage of my life.

I don't think I would take a lower level with kids, again, it was too confining for me, plus it is right by the bathrooms, and they do get unpleasant towards the end of the trip.
We all suffer from motion sickness, but we took meds before getting on board, and none of us had problems.
We had a fabulous time, and we are probably going to go to FL again before my oldest goes to college, just so we can do the autotrain again. Next time though, we will probably head to the beach for the week and skip the expensive parks, maybe hit HP but that is it.