Have you ever done a dolphin swim before? Some folks, who have done swims in the Caribbean or other places, may find the actual dolphin swim portion of Discovery Cove a little less intensive than the ones they've done previously. There's very little deep water interaction and no 'free' swim. If you've done a more in-depth dolphin program at another facility, this one may be slightly less rewarding in those respects.
However, I highly recommend Discovery Cove!
They take extremely good care of their animals (the same cannot be said for some of the less regulated facilities outside of the US, like the Caribbean & Central America) and put a high priority on the animals' welfare.
The park itself is just breathtakingly beautiful. It doesn't take much imagination to feel like you're in a remote tropical paradise. The service is impeccable and they really go out of their way to make sure you have a good experience.
The coral reef and ray pools are really awesome experiences. There are TONS of fish in that reef! The ray pool is something you could stand in all day and never get bored. The aviary, too, is amazing! Even if you skip the dolphin swim and just enjoy the rest of the park, you're certainly going to get your money's worth!
Even after around seven trips there (and working there for a while, too!), I still plan on going back again this year. If that's not an endorsement of quality, I don't know what is!
=)