For what we have done and what we plan to do at CC i see no need for a cabana. I am sure if we had one we would find it nice.
While at CC we got a few chairs near Pelican Plunge which was ideal for us as the kids loved the water slide and my husband spent almost his whole time on the island in the snorkel lagoon (which he got a very lovely sunburn on his back for). We were close to washrooms and cookies too as well as sandy beach and tram stop. It was a great day and we hardly left that area. Next time I hope to explore the island a bit more (bike ride, take the tram to serenity bay to check it out, maybe stingray adventure, etc) and don't have any thoughts of leaving before last call!
For myself I don't particularly see the value in a cabana when most of those amenities are available for the price of your cruise already, just a few steps farther away. I don't need the privacy and quiet or a private shower, if thats what i wanted I'd go to Hawaii instead. Now if
DCL would install some lockers for valuables, life on CC would be absolutely perfect.