The Rapid Traveler received his Global Entry card yesterday. Already a Global Entry member he added the card on a lark, though it has little practical benefit for him as it is only valid for entering the US by Canadian and Mexican land borders. It is not even valid for entering Canada via the NEXUS lanes or airport kiosks. But, he is a fan of the passport card as a backup government-issued ID (see uses for it here) and thought this might be similarly useful in a pinch. Looking at the card, he feels the $15 to add a card to his existing Global Entry membership was not worth it (cards will be issued for no additional charge to new Global Entry applicants).
Here is a sample card and the latest CBP announcement: