just back from BWV we too LOVED the drink refills at POR and purchased them on every trip.
Alas, I agree with many posters that it is NOT convenient to refill the mugs at BWV. The pool bar is not open late....they would pour the soda into a dixie-sized paper cup and it wouldn't even fill the mug. Of course I would then ask for an additional cup so I could at least have a full mug and troop all the way back to the room. (the mugs are the small coffee sized ones)
Refilling from the bakery was the exact opposite although a longer hike. Open until 11 pm, they would give you a full sized paper glass of pop (equiv of a 'large') which contained more soda than would fit in your mug. I much prefer that problem. I wish they had a refill station somewhere on the BWV.
from our experience, the bakery workers were much more accommodating when asking for refills. I found the bar tenders a bit snooty

when I asked for refills. (not that that stopped me from trooping up there with four mugs)
In retrospect, I would follow the advise of Deb and Bill and buy soda for your room. We spent over $50 for our 4 mugs and had to work to get them to pay off.