Of the two Universal parks, Islands of Adventure is the one more oriented towards thrill rides. As with many (most?) large parks, the park is divided into multiple themed sections, in this case they're known as "Islands."
Universal has something called Universal Express. The simplest explanation is that, for an added fee, riders can skip over long lines. This is a major benefit on the most popular rides (e.g. Simpsons, Hulk, Mummy). In practice, it means that you can often ride after waiting 2-5 minutes while people waiting in the normal lines are waiting for 30-60 minutes. One of the prime benefits of staying onsite at the resort is that our hotel room key served as a Universal Express pass, or, as we came to call it, the Pimp Pass.
The area just beyond the gates is The Port of Entry, with theming meant to suggest maybe Morocco in the 1930's. It really seems like something right out of an Indiana Jones movie. You walk down a broad street of shops and restaurant's that leads up to an intersection that you can follow left to Marvel Super Hero Island. There are lots of Marvel-themed buildings and characters walking around here. As you would expect, you can pose with the various characters, get autograph booklets signed, and, of course, buy lots of licensed merch. If you stick around long enough, you'll witness a crime alert and you'll get to see all the Fantastic Four rush off on ATVs. :)
There are a number of big-ticket rides here, starting with a well-done Spider-Man dark ride, Dr. Doom's Fearfall, which is a 200+ foot tower drop, and the centerpiece, the Incredible Hulk coaster. I consider myself a bit of a coaster connoisseur, but I have to say I admired the Hulk coaster more than I enjoyed it. To be honest, it's a pretty harsh ride. There seems to be a lot more head and neck movement than I'm used to on most coasters. Whether this is due to the amount of G's the riders are subjected to or suboptimal seat design I couldn't tell you. That said, I of course rode the thing 5 times. Sigh.
Continuing on counterclockwise to the next Island, you reach Toon Lagoon. This area features some pretty great graphic design in the theming of the various attractions and buildings. We were lucky enough to be greeted by some unbelievably blue skies as we entered this Island (the skies finally cleared after a day and a half of haze.) As beautifully blue as the skies are in these pictures, they were even prettier in person.The primary rides in this area were water rides, which means we skipped them our first couple of days at the resorts (temps were in the low-mid 60s) Dudley Do-Right's Ripsaw Falls and Popeye and Bluto's Bilge-Rat Barges were, very, very wet. Let's just leave it at "walking around in wet denim for hours"...
Next up was the Jurassic Park Island. There are two primary rides here, a Jurassic Park river ride, which is a water ride complete with animatronic dinosaurs, and the Pterandon Flyers. The Pterandon Flyers consists of a fairly tranquil suspended coaster that has an unfortunate flaw. Whereas most of the coasters at the two parks are capable of moving 16-32 riders per train, the Pterandon Flyers only moves 2 people at a time, and, at least the day we rode it, they seemed to be keeping about 45-60 seconds between cars. Ouch. Our only substantial wait for a ride at either park happened on this ride (the Pimp Pass wasn't honored here, either.)
Between the Jurassic Park Island and the Lost Continent Island there's a bit of a transformation taking place. The Dueling Dragons ride (a racing coaster) is in the far corner of the park, but there's all sorts of new construction around it. A new Harry Potter Island is scheduled to open there next year. It's pretty obvious that the Dueling Dragons ride will be part of the Harry Potter Island once it's completed. Anyhow, the coaster's pretty cool, and it'll be even better once the theming is completely integrated into the new Island.
The primary attraction on the Lost Continent island was Poseidon's Temple, which basically consists of a really impressive building constructed around an interactive show. There was a pretty funny and embarassing anecdote involving lemmings and emergency exits here that I think I'll leave for another day.
The last of the Islands is Seuss Landing, which is thoroughly impressive graphically. It really did feel like a Dr. Seuss book brought to life, with wonderfully curvy skewed buildings, brighter than bright colors in a riot of whimsy. As you'd probably expect, this attractions in this area are primarily kid-oriented, but there is plenty to enjoy here for any adult who grew up reading these classics.
In all, we spent 4+ full days exploring the parks so we really did see pretty-much everything. Though you trade off a bit as far as weather, I would stll recommend mid-December as one of the best times for adults to visit the Florida parks. You can usually find nice discounts and the crowds are far smaller than during peak season (which means you get to see and ride a lot more.) There's probably lots more I could talk about (the cool fingerprint-locker system, the exhorbitantly-priced food, comparisons with Disney), but I've probably rambled enough. Next up: a visit to "real Florida" when we spend a few days at my parents' home.
An ounce of application is worth a ton of abstraction.