I've never seen it not busy. I think the worst time is right after park closing. You can also fill up the mugs at the pool snack bar. Some people have said you can get them done at the lounge and sit-down restaurants, but I felt a little weird about that and never tried it. There is no place to fill them up yourself and my experience is that you pretty much always have to wait to get them filled. The refillable mug program does not work as well as yc/bc as it does at the other resorts. I would not buy them if I had the decision to make again, BUT we drive so have a cooler with water, soft drinks, etc. in the room. If you do decide to get them, keep in mind that you'll save a dollar or so by buying them at Beaches or Hurricane Hannah's instead of from the room mini bar. You'll also have the full color choice instead of just what was stocked in your room.