My wife and I stayed at the GC Marriott last November for one full week. I used points to get the free room but ended up paying $20 per day. I asked for ocean view as an upgrade and was able to get it. The beach front is rocky and there is no sand. We arrived just one week after a hurricane passed through so things were disturbed. I liked GC as a place to visit as the income level is much higher there....no people bothering you while you try to relax. It's expensive to eat, but you will be on vacation. If you like beaches, then 7 mile is the place to be. You can't really walk there from the Marriott. Choose the Hilton, Westin or even the Holiday Inn. Actually, the Holiday Inn has great access to a public beach across the street. It is a brand new hotel that looks good for a Holiday Inn.
Overall the Marriott was O.K. This property is NOT a full resort. It's on the smaller end and is much more like a Courtyard. They have a resturant, but never ate there. At $25.00 an entree, I thought it was expensive compared to other places nearby. The Turtle Farm was destroyed in the Hurricane. I'm told it is a really neat place to visit, but all the turtles washed to sea.
Overall, GC has great scuba and beaches. It's a relaxing place that is worth the visit.