We have spend a week at the Thalasso. In fact never felt the urge to shuttle to the main island.
Note that we did explore the main island for 4 days before heading to the Thalasso.
Its my third trip and I;ve tried the Moana and its on my do not return list. I like renting a car and driving round the road and just having time to stop and look at my own pace; plus chance to go to store for provisions etc makes the ferry useful. The resort Is nice but I would go crazy if I were there for a week. Hate to say it would be nice to have resort fee, some hobby cats and the ferry in the fee...