I rode Slingshot for the first time last friday and what we did was pay for a ticket, and they gave us a timeslot (we came pretty late in the day, about 7:30, so we just went with the earliest timeslot. I guess you could pay at the beginning of the day and then reserve a slot later in the day if you wanted). They gave us a receipt and wrote down the time, and we got in line at that time to ride. It's supposed to make it that you don't have to wait in line, but even though our timeslot was 8:15 we ended up riding at around 8:35. I guess it gets backed up a bit.