We really love this service! We end up with great shots that we could never get otherwise and then you can even add borders with the year on the finished pictures.
When you go into one of the parks, you'll see lots of photographers snapping pics of guests posed in front of the castle, for example. You can ask one of them to take a pic of your group or they may approach you. It's all free at this point. After taking the pic, they'll give you your PhotoPass - like a credit card- that will hold all your pics for your entire trip. Every time you want your pic snapped by one of these photographers, give them the card and they'll put your pics on it. Then you can either go to a designated shop to buy them or you can take the card home and look up your pics on-line. That's when the cost comes in. You can buy just individual pics or purchase a cd of the whole card. I read that you can also do a calendar that includes 13 pics. One woman saved alot by purchasing the calendar instead of individual pics - it can get pricey!