On our 7-day we had week-long passes and the number of people there was different just about every time. Once, it was just the two of us, but I went without my wife one afternoon, and there were probably about 20 people total in the various rooms.
I completely enjoyed each trip, though. (The time that it was really crowded, I ended up participating in two really interesting conversations. One was mostly about DVC, and the other was with a former crew member who was doing the cruise for the first time as a passenger.) When it was crowded, people are more likely to talk to each other, when there are just a handful of people, they tend to ignore each other. (Both have positives & negatives, but in general there are few negatives in the Rainforest Room)