We are just back, and our day at Discovery cove was the highlight of the trip. After fighting people, crowds, and all that not so fun stuff, it is a wonderful change of pace. If you can, GO!!! Our family and our friends traveling with us, thought it was worth every single penny. Remember, you get a free ticket to either SeaWorld or Busch Gardens, and the lunch they give is very good. When you factor both of those in, the price is easier to swallow.
I third getting there early. We got there at 7:55, and were not the first ones there-but we still got a 9:10 swim time. By the time we finished the dolphin swim and looked at our pictues and everything-it was nearly 10:30 - it does take a good chunk of your day. Also, there are few clocks in the park-it's a bit hard to keep track of time. You can wear a waterproof watch if you have one!
In other words, we thought it was more than worth it!!!!