We were at Universal Saturday and Sunday, Dec 4 and 5 (first timers here). We spent Friday at Epcot, and it was a madhouse, I was expecting the worst for Universal the next day. We did not get out there until noon, so we thought we wouldn't even attempt to go to Harry Potter that day, and went to the Universal side. We were pleasantly surprised that we were able to get on several rides, including Simpsons and MIB with little to no wait. At around 3:30 pm we decided to just go to IOA to check it out, maybe take some daylight pictures of Hogsmeade. We were also hungry, so we thought maybe we would try our luck at Three Broomsticks. Well, we walked right in, got our food and were seated immediately, it was maybe 1/3 full. Although the area looked crowded, we could go into all the stores except Ollivanders. The posted time for FJ was 45 minutes, so we decided to do it: it was more like 25. After this, posted time for Dragons was 10 min, but my sons were able to walk right on. Sunday we did the same thing, went to Universal side first and did not get to HP until 4:15 pm, and it was even less crowded, there was little to no wait for anything except Ollivanders.
We spent 2 days at this park, no express pass, got there around noon both days and were able to do every ride and show we wanted to do at least once, many twice, and left before park closing both days.
RE FJ and motion sickness: I am sad to have to tell you that it was a bad one for me. I am a severe motion sickness sufferer, but with Bonine I am able to ride mostly everything at Disney, including tea cups. I have not braved MS, so I can't comment on that, but had no problems anywhere else other than a little queasiness at Star Tours.
Well, my luck did not hold at Universal: the first problem was at the Simpson's ride: I had to close my eyes half-way through it and felt a little bad for about 15 min after, but got over it. FJ almost killed me, I had my eyes closed the entire time and barely made it off the ride, through the store and across the way to the bathrooms before getting quite sick

Oh well, at least I tried, and it was great just being there and going through the village and the castle. My sons of course loved it, they did not inherit my queasiness and can do all this stuff over and over.