I just used it for our trip last week. We got around 130 photos out of it, plus stock photos they include for you as well.
1) you get photos for each time you ride. We did ride RSR five times, lol, and we've got five different photos. If you plan on riding attractions with photo options multiple times this can definitely be a benefit.
2) something I was warned about prior to buying by people here was that character photo ops don't always have Photopass photographers. We were there over the 60th, so we may have just gotten lucky, but we only had one instance where we had to use our own cameras, but keep that in mind.
3) if you get it, take advantage of the Photopass locations for maximum photos. Again we lucked out here since there were additional photo spots for the 60th anniversary, but even if you do the regular ones (esp. for both day and night shots), you can get your money's worth.