So, what is it? I've seen pictures and I know there are rides but... isn't it just like 1 strip of Diagon Alley? And some little shops? Or is it all of Islands of Adventure with a TON of stuff to do? I'm not a huge Harry Potter fan but I'm very interested to see what the 'immersion' experience of it.
Before I went, I really thought I was going to be disappointed because people seemed so excited I was going. It's Diagon Alley, Hogsmeade, and the Hogwarts express. Both parts have a dedicated Harry Potter ride, but the whole experience they have put together is really incredible. There are all these details in the store windows, Knockturn Alley, and little easter eggs (like Kreacher appearing out of the window at Grimauld Square every few minutes). They did an amazing job of making everything look just like the movies/books. There's a vanishing cabinet in Borgin and Burkes and you can hear a bird chirping in it. The shrunken head on the knight bus talks and jokes with you. Waiting in line for the rides is also awesome. They recreated the lobby of Gringotts to a t. Plus, there are all these "spells" you can do throughout both parks and that gets you talking to the people who work there and other "witches and wizards" (It does also pretty much guarantee everyone will plunk at least 50 bucks on a wand, but I borrowed mine from a friend). Diagon alley is hidden in London just like the books. I was not as impressed with Hogsmeade. It looks awesome, and the three broomsticks/hogs head is great, and Hogwarts is super cool, but they really improved on everything when they built Diagon alley.
So yeah, totally nerded out.