We just did Uni for the first time last weekend. We ended up having to go three mornings to get the few things we wanted to ride done. We started in Universal Studios two of the mornings and IOA one of the mornings as, even though we were there early, Gringotts was down all three days for a long time. When we got there the second morning, the cm said it had been down since they opened for resort guests at 7, and he didn't know how long it would be before it was back up. The wait was at 110. This was at close to 10. This ride is very intense. We finally got in the single rider line the third day and my daughter was able to get on within 15 minutes even though the standby was at 60 minutes. Make sure and do the single rider line if it is open. They close it when the stand-by line gets too long.
My daughter was able to get on Forbidden Journey two of the mornings we were there (walk-on once and 10 minutes the other time, but the other morning the Hogwarts Express broke down and we were in line at King's Cross, an hour before they even told us that they didn't know when it would be back up. They finally kept saying 15 more minutes. The workers couldn't even figure out the problem. They would stand in a huddle and try to decide what to try next. We made it all the way to loading when they said it would be 15 more minutes once again. We were too tired of standing, after five days of Disney and Uni, to stand another minute, so we asked for a pass to another ride. They asked which ride we wanted and actually called the cm at Men in Black and told them to let us go through the express line. Which they did. One of my favorite rides there. Even with motion sickness problems and a bad back, I had no trouble with this ride.
They don't offer us a front-of-line pass, like Disney does. You have to ask. Most people just walked out after all that waiting.
I recommend starting at Journey (save the sightseeing for later), then catching the Express to the Studios as there was never any wait at all going from Hogsmead to Diagon Alley, but we had to wait both times we tried for a long time going the other way. We never did get to do the Studios to IOA way, which I was told is the more exciting way. It is different both ways. We did the IOA to Studios way twice. There is a really neat effect in King's Cross Station when you get close to loading where it looks like you are going through a brick wall. If you want a picture of someone going through, you have to stop a ways back and let the one who will be in the picture go ahead so you can take their picture. I videoed my daughter going through. It really looks like she goes through the wall.
The restaurants in both areas are ridiculously priced for what you get. We couldn't believe the breakfast platter that is only around 8 at Disney is 16.99. Lunch was just okay. My daughter loved the butterbeer. She got it twice.
Her favorite ride, ever, is Forbidden Journey. She loved it. She told me that if I take something for motion sickness, that I'll love it too. She said that it is a very smooth ride that wouldn't hurt my back. I may do it next trip.
Be careful about opening times on their app. It said that Universal Studios didn't open until 9, but it opened at 8. We knew it opened at 8 on Horror Nights, but this wasn't a party night.