The attention to detail
The attention to detail, knowing when to go to certain locations to avoid crowds, the skill of the Panga drivers, and the knowlege of the guides/naturalists about the unique wildlife. That said, I was a little disappointed with the one day when we went to the Darwin Center and then to the "ranch/farm" to see the Tortoises, as we had already seen them "in the wild", but it appeared as though every trip/boat was in some way "required" to do those activities. Would have preferred a snorkeling option for the afternoon on Thursday.