Yes, we have. Just take them to the purser's desk and ask them to apply them to your onboard account. No problem!
Carnival x9: Sensation, Paradise x3, Legend, Destiny, Conquest, Pride, Holiday, PLATINUM: Dream 9/11/2010
RCL x5: Majesty of the Seas, Sovereign of the Seas, Freedom of the Seas, Liberty of the Seas, Oasis of the Seas
Celebrity x1: Century
Princess x3: Caribbean Princess x3, Dawn Princess
NCL x1: NCL Spirit