Its definatley worth it, even just for the one experience. We went in 2004, and although I probably wouldnt want to go again, just for the fact that we did everything, we loved it. Theres not much of a chance in everyones lives to swim with sting rays, tropical fish, and ofcourse dolphins, and its something you can look back on and if your anything like me, you'll be glad you experienced it.
However, saying that, If your not a fan of swimming or dont intend to do the dolphin swim, theres very little on offer, apart from sunbathing, which may seem like a waste of money.
I'd also recommend purchasing the dvd, its shot beautifully and really is a great watch. As well as this, it may be useful to buy a disposable underwater camera before you go, I dont think you can take it in the dolphin pool, but you can use it with the sting rays and the tropical fish coves.
Hope you enjoy!