They originally added the Freeport stop to the 4-day after we had booked (11/00). There may have been changes since then, but it was just a boring industrial port when we docked and required a bus/taxi ride to get anywhere. We chose to treat it as a day at "sea" anyway, and didn't even get off the ship. DSs spent most of the day participating in the Lab activities, DH and I spent some time out on Deck 10, then he did the wine tasting and I played Bingo. It was a great, relaxing day!
I wrestled with the feeling that I should at least set foot on the island so I could say "been there, done that", but in retrospect, our choice to stay on board was a good one.
Whatever you decided to do, enjoy!