I hope my information is helpful:
We pre-purchased the PhotoPass CD last year for $99.95 (I believe) and it was well worth the price, in my opinion. We had well over 200 photos taken of us and we got to download them all on CD.
This year we already purchased the PhotoPass+ package for our upcoming trip in September. The difference here is that you get to include on-ride photos from all the E attractions as well as photos from Character Meals.
After you purchase the package online, you are sent a voucher (FedEx 2nd Day Air) for a PhotoPass+ card that is redeemable upon check-in at your hotel. I am not sure, but it is probably different looking than regular PhotoPass cards. This way, you can be recognized as not having to purchase the on-ride photos or the Character Meal packages. You are also given an Authentication Code for when you want to redeem your photos online. You choose the photos you want to put on the CD, and when it is time to check out, just enter the Authentication Code and it will credit you the amount you were already charged when you prepaid.
Like I said, I thought it was totally worth it. I don't really like Point and Shoot cameras because I rarely get good shots (we bring one anyway). At least with this, we can take family photos that look professional in front of all major sightseeing venues at the World.