I find that people really don't give the theming at Universal enough credit. Even with HP aside, the rest of both parks is extremely immersive.
In USF, Production Central is supposed to look like a studio because it is. It is the largest working production facility outside of Hollywood. They still shoot commercials, television shows and films in those soundstages. The New York section is beautiful.. in my opinion, better than the one at DHS which lacks depth and looks way more like a facade. I love the alleyways in the USF NY. Even though I'm not a Simpsons fan, I think the Springfield area looks great and offers a ton of great eating choices. Also, many of the queues are wonderful, even if the show building isn't- Despicable Me, Mummy, Men in Black, E.T., etc... really immersive queue lines.
Islands of Adventure is also beautifully themed. Port of Entry has so many fun details if you stop to look. Seuss Landing is really well done, with bright colors, no straight lines, so it's as if you're walking through a Seuss book. The Lost Continent has some spectacular architecture, particularly Mythos (the inside is incredible) and the Poseidon Fury show building.
I believe they're going to do an amazing job on Diagon Alley, from the pictures I've seen. Hogsmeade and Hogwarts are spectacular and I can't see why this wouldn't be just as good. For people complaining about crowds, yes, Hogsmeade could be crazy busy but there are many times during the year where it isn't nearly as busy. I've seen just as big crowds at MK.