Hi, we just returned Sunday and used the dining plan. Most restaurants added 15%, but I think at least one added 18%. We always checked, and if we had excellent service, we left a little more to make it 20%. There were only 2 meals we didn't leave any extra. The service wasn't bad, but there was no extra effort. Not even an 'Are you enjoying your stay?' We had some great servers and loved using the plan.