As a longtime Harry Potter fan, I obviously had very high expectations for Universal when it came to expanding into a theme park environment. They succeeded beyond all expectations.
Hogsmede and Hogwarts are painstaking recreations, often to the detriment of crowd flow (the small streets and stores often result in a traffic jam and the crowds have only just begun to die down since opening, but J.K. Rowling was adamant that they match the films), and the area is filled with interesting storefront displays, animatronics, and small details in every nook and cranny. The Butterbeer is brilliant and the perfect refreshment, and the Three Broomsticks serves rather generous portions of typical British or Americanized British cuisine for its price.
Of course, the big draws are the rides. Flight of the Hippogriff and Dragon Challenge are rebranded rides from the old Lost Continent days, though both are rather good in their class (Dragon Challenge unfortunately has disabled the dueling aspect due to some unjust paranoia), but Forbidden Journey is literally a ride like no other. While other rides have combined live action set pieces and screens (The Amazing Spider-Man on the opposite side of the lagoon does the same), no other uses the articulated arm and combines it with a track to allow for an unprecedented freedom of movement and an extremely unique experience. Just keep in mind that while Harry Potter has mass appeal, the ride is probably not recommended for anyone 10 or under; it's filled with scenes that tend to scare or surprise even adults, and the Dementors are probably guaranteed to cause nightmares for anyone not old enough to tell fact from fiction.
If you can handle the crowds, the Wizarding World of Harry Potter provides a unique experience even beyond the obvious draw of the series.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.