Also, the mini-bar exchange for two coffee cards is a great deal as the cards are typically unmarked. (Most actually are if you get them from a server you have made friends with during the cruise.)
In fact, I've only had one card marked in the past several cruises...
I agree. Try also to get an unmarked card when you buy a coffee card at a bar. That unmarked card may turn out to be the brewed coffee and hot chocolate gift card that keeps on giving on your future Princess cruises.
I'm not sure about the "new" cards that their issuing lately if they're going to be pre-stamped or not. I heard about them but haven't see one yet. We've got loads of the old style cards with no date or ship name on them so they'll be good only for punches & not for unlimited regular coffee or tea. Oh well.
It doesn't make that much difference on the Regal & Royal anyway since all the regular coffee is the same no matter where you get it.