I think this will turn out to be a bad idea for Carnival (charging the 3%fee, like Princess). On our New Year's cruise on the Golden Princess, I saw many players approach the tables and ask for chips on their ship's card, yet when they found out about the 3% service fee, they passed, and didn't bother playing, or took less than they planned on, and didn't play as long as they likely would have.
Even discussed this with the Casino manager on the Golden, and he thought it was a pretty major deterrent to many players.
My "bet" <G>, most people would loose more with the "free" money system, than the 3% service fee will make up.
I do however like the Ocean Player's Club. If you play the higher stakes, at least you get "something for your money"<G>. I've got a certificate for over $900 to get myself started on our CruiseMates Legend cruise in Jan.
Now if only the cards will co-operate I won't have to worry about the 3%... though I will miss all those FF miles.