Neither Twister nor Poseidon are the most popular choices. I think of them as more minor attractions such as "Sounds Dangerous!" at MGM and "Gran Fiesta Tour Starring the Three Caballeros!" formerly El Rio de Tiempo. I'll hit them if I have the time.
It sounds like you missed some of the best attractions when you went. These seem to be the most popular rides and shows:
Universal Studios
Revenge of the Mummy
Men in Black
Shrek 3-D
Jaws
Terminator 2 3D
Horror Makeup Show
Islands of Adventure
Spiderman
The Incredible Hulk
Dueling Dragons
Popeye & Bluto's Bilge-Rat Barges
Dudley Do-Right's Ripsaw Falls
Jurassic Park River Adventure
The Cat in the Hat
If you missed any of these, then you didn't get a complete picture of what the parks offer. I'm sorry that DD was down when you went but most likely it was open again during the day. Sometimes, rides do go down for whatever reason. I've been on Test Track over a dozen times and so far have only ridden 2 or 3 times. I swear that I must jinx that ride because I stand in line and it goes down right before I get ready to load the ride. Now I refuse to go near it as I feel sorry for all those people who are waiting in line knowing that I will be the cause of them not getting on.