We were there from 11/1 - 11/7 when the mugs ended and the drainage problem supposedly occurred. I say supposedly, because I was oblivious to it. We were spent a good deal of time walking around the grounds while we were there - going to and from places - and never noticed any drainage issue. We didn't have any problem in our room and didn't see any sewer crews working or anything. So whatever happened, happened without my knowledge.
As far as the mugs go, if I hadn't been able to get one, I probably would have been disappointed. But, they were one of those things that we shouldn't have purchased. We definitely didn't get our moneys worth. We aren't coffee drinkers so that's probably part of it. We would have been much better off to just buy soda from the vending machine. It would have been easier too. The only good thing about the mugs was drinking hot chocolate from them while we watched the fireworks on the beach.
Whatever the drainage problem is will surely be resolved by the time you get there. Disney doesn't seem like the kind of place that would let that go.
Go and have fun. I just got back and all I can think about is going again.