We redeemed a GAD voucher late this afternoon (about 4:30 pm) to get fastpasses at Epcot. It was a very quick and easy process, and the fastpasses were great! There were just two of us, but the CM gave no indication that a larger party would have been an issue. I know there was a thread on this at one time (can't find it now) so I just wanted to pass along our experience, for what it's worth.