I've taken them all and I would say that if you have the least interest in animals they are very much worth the price.
I would rank them in order as Rescue, Polar Expedition, and Predators (the new name for the Sharks tour).
Unfortunately, my favorite bit in the Rescue tour is no longer there (unless they've put it back, which they should). On the way to see the veterinary operating room, you used to pass cages filled with rescued and abandoned parrots, that who squawk "Hello! Hello!" as you passed by.
Then on your way back, they'd squawk "Goodbye! Goodbye!"