We LOVE Islands of Adventure. It is our favorite place to go for vacation. This place is a feast for the imagination. You get to travel from Marvel Super Hero Island and ride the Hulk coaster and Spiderman; Toon Lagoon and the water rides Popeye (bring your rain poncho or get soaked to the bone!), and Dudley Do-Rights log flume ride; Seuss Land to immerse yourself in the world of Dr. Seuss; Jurassic Park and interact with T-rex as well as face one down before going down a waterfall; Wizarding World of Harry Potter to fly with Harry and the gang (maybe once- not the best ride if you get motion sick but the walk through is a MUST no matter what) and enjoy the dragon challenge coaster- blue is best front row; red is best in the back.
The Lost Continent is for shows. Poseidon's Fury is a relief from the heat. Sinbad is a fun show with lots of laughs.
If you stay at a Universal resort you can get unlimited access to express rides and shows. This is quite a time saver! You can also purchase express pass when you enter the park. If you must do Harry Potter, consider staying at a Universal Hotel as you get access to this part of the park one hour early all week. After this, Harry Potter Forbidden Journey and Olivander's wand shop have long waits.