I think for UK travellers who tend to go for at least 14 days photopass is a good deal.
We've done it twice - definitely pre pay so you pay $99.
Basically you get a card and everytime you see a photopass photographer make an effort to get a photo. Particulary at
MNSSHP if we told them we had prepaid they took lots of pics.
Also ask about magic shots - things like pretending tinkerbell is on your hand. If you find a quiet phoographer they are more likely to play around than one with a big line.
We didn't see any at waterparks but went october they are there peak times.
Also at xmas there was a photopass photographer doing formal pics by each xmas tree in the hotels - we saw families in co ordinating outfits obviously having pics done for gifts for family.
If you do BBB they will take posed shots at the studio at either DTD or in MK and add them to the photopass card for no extra charge.
When you get back you go online and can add borders etc to the photos then order your cd with the pics on. cd is posted to you.