We have been here for the past three days (11/22, 11/23, and 11/24). Overall, I would say the parks were less crowded than I expected; however the crowds are not evenly distributed throught the park. By far, Diagon Alley and Hogsmeade are the most crowded areas...we are talking elbow to elbow (it's worse in Hogsmeade). Today was the most crowded day of the three. I would not have characterized yesterday as a two, but we did not wait more than 20 min for anything. We did stay at a Universal hotel and had express passes, so that decreased our wait times dramatically.
With that said, we only did early entry on one day (11/22). We used early entry to ride Gringotts 2 times in a row - the first ride was essentially a walk on, and the second was about a 20 min wait. By the time we got over to Hogsmeade, we had to wait an hour for Forbidden Journey. Everything else in the park that day was essentially walk on for us, using express pass.
Yesterday, we saw the wait for Gringotts get up to about 90 min. But we did single rider during that time and were able to ride twice with no more than a 10-15 min wait both times. With express pass, most other things were walk on, except for the Shrek and Minion rides, but those waits were due to the fact that those rides are actually shows with a fixed theater capacity. So you have to wait for the previous show to finish. We did not get to the park until about 830 am yesterday (didn't take advantage of the early entry hour from 7-8) but that did not affect our ability to ride anything.
Today we entered IOA right at 9, with the rest of the crowd (no early entry). By the time we got to the back of the park, the wait for Forbidden Journey was 20 min; by the time we exited the ride, the wait was over an hour. I noticed that the places to eat seemed to have much longer lines and slower service today. That's probably where we spent most of our time waiting. We didn't ride Gringotts, but the wait was over 100 min. Everything else was walk on for us, with express pass. I noticed the Minion ride had a 70 min regular wait, and other rides like Mummy and Men in Black had 30 min regular waits.
As I said, the crowds were lower than I expected, but certain areas of both parks do feel much more crowded than others. Since we planned 3 days in the parks, we were not rushing and were able to enjoy everything we wanted (some multiple times) with minimal waits.