The question of whether the Carnival Cruise MasterCard is a good card or not depends on how much you spend on Carnival Cruises every year.
As with most travel affinity cards, you get to earn double points on for every dollar that you spend on Carnival. And in terms of the value of points, it is worth 1%.
Under most circumstances, I would say that if you take your vacation with Carnival, this would be the card to get. But our task is made slightly more difficult because other cards like Discover and Amex also offer the opportunity to either get discounts with them or use their points at the same rate as their own Fun Points.
The case of Discover is pretty interesting. You can a 5% rebate when you book a Carnival Cruise through shopdiscover.com. To me, that is the same as getting a 5% discount. That is clearly better than the 1% value that Fun Points provides.
One of the advantages that Carnival has is that their MasterCard allows you to earn double points on their purchases. But Discover makes up for that by allowing you to double the value of your rebates with a Carnival gift card. That is almost like getting double points on all purchases! And Discover also gives you the opportunity to earn 5% cash back through their rotating categories and online shopping partners.
The case of the Amex platinum is also interesting because you can get room upgrades and get a $400 ship board credit. Unfortunately, there are no perks for Carnival Cruise but ironically, they are available for Princess, Cunard, Holland America and Seabourn (which Fun Points can be redeemed for)
Given these alternatives, I find it hard to wholeheartedly recommend this card even if you travel with Carnival. The card is ok. But I would give series consideration to the Discover More as I think you get better value in terms of money you can save with Carnival.