A trip a few years ago we didn't have them and it seemed like DS wished we did. I didn't get them because they seemed unnecessary and I didn't want to spend the extra money. For the trip we did last week (now DS is 21) I asked him if he wanted me to get some because he seemed to think they were really neat last time, but his answer was (no - not worth it) -- it's really easy just to keep track of the ticket card.
They look pretty cool, but DS and I both on two different occasions thought of them as being extra money not worth spending. And DS said that even when it was my money lol.