We stayed at the Westin and ate at Cruz Bay Prime one night when we were too tired to go into town.
We didn't have a reservation but it was easy to get a table. The view from the restaurant is really great, I would recommend going up there just to see how pretty the view is.
Since we were on vacation and didn't want to deal with leftovers, my husband and I split a 16oz ribeye, a salad and some sides and it was the perfect amount of food. Their mac & cheese is sooooo good.
If you like steak and want to have a nice meal, I recommend this restaurant.