Really, since all DVC resorts have fridges and coffe makers, it is cheaper and better to stock your own beverages in your room. I also found most DVC refill stations to be less convienent / farther distance than I feel worth while for a morning or after a park day refill.
I guess if you are at a DVC pool with a pool bar refill station (there are a few) and frequently use the pool during bar open hours (noon-early evening) you may get your moneys worth.
It is cheaper to stock your own beverages in your room, but if you have the quick service dining plan they give you a mug. We are getting them when we go next month with our dining plan so we are going to use them. Plus it makes a great souvenir to take coffee to work on your commute.
It's one of those, "It depends" situations. As long as our stays are (24 nights) we definitely get our money's worth from the refillable mugs. They probably lose money on us. One of us will do a coffee run while the other is in the shower, getting ready or whatever.