I thought this idea died after the pilot program, but I guess not!
My one and only concern is split stays. The FAQs in this article make it sound like all mugs not purchased for 1, 2 or 3 days will be good for at least 14 days and won't expire at checkout. If that is so, then that's good news and takes away my concern.
Also, I am VERY pleased to hear that they can be used at any resort beverage station and not just the resort you check in at (as that would also cause an issue with split stays).
So, as long as the info in the FAQs is true and they don't decide to change anything, then sounds okay.
However, we will not be getting these without the dining plan. The mugs had already increased since our last stay and now they want $18 for a length of stay mug? That is over $100 for us, so we will probably pass.