At Aulani, Guaranteed Week Owners can opt out of their fixed week each Use Year, if they wish. If they opt out, their week is converted to traditional DVC points equivalent to the number of points they purchased less the 10% premium. For example, if they purchased fixed week #52 for 655 points, they can opt out of the fixed week and receive 595 points.
Those 595 points can then be treated just like traditional DVC points. They are considered Aulani points, so they can be used to book stays at Aulani during the Aulani Home Resort period. They can be used to book stays at other resorts beginning with the 7-month window, or exchanged into
DCL, ABD, RCI, etc. Or they can be banked into the next UY. BTW, a Guaranteed Owner could even opt out of their fixed year for the next UY and then borrow those points into the current year if they wish.
With this flexibility, a Guaranteed Week Owner would not necessarily have to spend the next 50 years going to Disney at Christmastime. Also, this flexibility would permit a GWO to look at a calendar and adjust their stays in those years that a holiday doesn't fall in their fixed week. For example, Christmas falls in Week #51 in most years, but in 2016 in falls in Week #52. For that year the GWO could opt out of their fixed Week #51 and use their points to book another week at Aulani or another resort.
In terms of how a Guaranteed Week affects resale value, I don't know. I've never noticed an Aulani Guaranteed Week on the resale market, so I don't know if it will demand a premium over a comparable traditional deed.
I'm curious how popular fixed weeks will be at VGF. There seems to be a good number of Disboard members who go to WDW at the same time each year, like in October for the Food & Wine Festival, in March for Flower & Garden, or in January for Marathon Week. The Guaranteed Week Ownership would be one way that Members could lock in their reservation each year.