I'm interested, too. We go on 1/20 and are trying to decide whether to use the GAD fastpass or just credit to our multi-day pass purchase. Want to know how many rides are on each pass and the limit on each ride with the special fastpass.
It is part of the Give A Day, Get A Day promo. If you already have tickets WDW is offering you three other options as a reward and a FastPass is one of them. I'm not up to speed on exactly how it works but some have said that it is comparable to the FP that were given during the YOAMD promo.