It is one of those things that is best answered with "your mileage may vary."
For people who go often, it may not be worth it. For those that are doing a special, or once-in-a-lifetime trip, it is a must. We go every three-four years, and we buy it...haven't regretted it. We usually end up with about a hundred pictures before we add embellishments...and we have uploaded them to online services to make calendars, posters, all sorts of things to remind us of our trips.
The ride shots are one thing, but more importantly if you plan to the character meet-and-greets, it is certainly worth it because you get these photos.
In my opinion, grand parents with all the grand kids...for several days...almost a no-brainer to me. the initial cost seems high until you see what individual downloads cost...if they might want more than 10-12 photos...it is worth it