A few thoughts about Diagon Alley.
1. Diagon, and ESPECIALLY Gringott's is the priority for nearly every single human visiting Universal this week. I've been opening day and twice since, and I've learned that the AREA is hitting capacity before park opening every day, which is nuts, and the only plus time to ride Gringott's is as early as possible. For anyone who CAN come during a lesser season (Early September??), probably a great idea.
2. Getting into the area after 9:30 or so is pretty easy and usually quick even with return tickets, but Gringott's regular queue isn't going under 4 hours and is running at maybe 50 percent of its capability (I've heard 4 or even 5 trains out of seven, but just one station and FREQUENT breakdowns). Everything that is new-Harry Potter that is also not Gringott's has minimal wait times at worst.
3. Everything at Studios other than Despicable has atypically light morning crowds. Only Rockit/Despicable/Transformers are getting even hour wait times in the afternoon. IOA is pretty light other than the water rides, I saw Forbidden Journey at 30 minutes at 2PM on Friday.
4. As for the land itself...The most immersive themed environment in Orlando. It honestly feels like you walked into a foreign country. Rediculous amounts of artwork/detailing/animatronics/interactive elements/new food options. The shops are incredible fun, and are clearly upgraded all around from Hogsmeade. Not comparable to New Fantasyland, IMO it's just excessively better in representation of the property. Little details and fan service just oozing from every corner.
5. As for the ride itself...MUCH clearer storyline than Forbidden Journey, and definitely has some new and interesting technical elements. Is it the clear world's best attraction I had hopes for? No, not really. It rides a LOT like transformers in the end, but again the theming is new-precedent-immersive which really propels the experience. It's certainly an A attraction, top 5 percent in Orlando.