Quick facts: There are 2 parks. Universal Islands of Adventures, which contains Hogsmeade (and Hogwarts), the original HP World, and Universal Studios, which contains Diagon Alley (and Gringotts), which just opened in summer of 2014. They are connected via, you guessed it, the Hogwarts Express. This means you need tickets to two parks to see it all. We got two-day two-park tickets (so we could go back and forth each day) and I really think this was the way to go. I fear we would have felt rushed if we only got one day tickets, but two days gave us ample time to see all of the Wizarding World, and the rest of the parks too! Including riding the Hulk multiple times and the Spider Man ride. (Which were favorites I remember from the time the Hopewell High marching band went to Universal when I was in 9th grade.) (I played the coolest instrument ever. I'll leave it at that.)
The details in the park are astounding! Waiting in line becomes an adventure in and of itself as you see the tri-wizard cup, the talking sorting hat, and the most realistic depictions of goblins ever while waiting in line! But, I do have one pro tip for skipping lines, especially if you've already seen all the decorations and you're re-riding: Find the Single Riders Line! As long as you're over like 4 feet tall (aka me since birth) and willing to split up from your party for the ride, this line moves SO much faster. It's often sort of hidden and you have to look for it and it takes a weird secret path but we saved so much time "cutting" lines through the single riders method. Do it!
The Hogsmeade rooftops are covered in fake snow* which is a cute touch since it seems so many magical scenes in the book take place in winter. Also, I've never seen "snow" next to palm trees before, but I could get used to it:
*my favorite type of snow
And, of course, we couldn't forget to indulge in butter beer. (Since people have asked, I think you could get alcoholic butter beer somewhere (maybe), but we went to the 3 Broomsticks in Hogsmeade and The Leaky Cauldron in Diagon Alley, and alcoholic Butter Beer wasn't really on those menus. But they did have frozen & non frozen. It was delicious!)
Have you been to the Wizarding World of Harry Potter? Would you go? It's safe to say it's the nicest amusement park I've seen, so I highly recommend spending a couple days checking it out. It also makes me want to re-read all the Harry Potter books, of course!
p.s. Don't forget your Harry Potter swag to wear in the park. (There were lots of robes!)