I have long recommended the Diners Club credit card because, despite limited acceptance and a hefty annual fee, the benefits were really unparalleled: an outstanding rewards program, two full billing cycles to pay, free iDine Prime membership, concierge services, and primary rental car insurance.

Needless to say, the anticipated linkup between Diners Club and Mastercard had me very excited. If my Diners Club card would get accepted everywhere that takes Mastercard, it would rise to a spot as my #2 credit card (behind the Starwood Amex). However, I’ve been nervous. I assume that the linkup with Mastercard would mean lower interchange fees for Citibank, which issues Diners Club in North America. And with lower fees I imagined cost-cutting from the benefits budget. Diners Club has assured the contrary.

I received an information packet in the mail last week, preparing me for the changeover which is anticipated in about three more months.

Lo and behold, the two billing cycles to pay benefit will be gone. There’s also an increase in the foreign currency conversion fee to 3%. And while a Diners Club rep tells me that the rental car insurance benefit isn’t going away, there’s a troubling statement in the brochure about a possible change in insurance carrier. I’m nervous about that benefit.

I’m more than a little peeved because I just re-upped with my annual fee this month. I’ll still keep the card and use it as my primary backup for merchants that don’t accept American Express as long as they keep the rental car insurance. But if that benefit goes away I’m not paying a $95 annual fee for a Mastercard with a versatile rewards program (that charges a fee for converting points into miles).

One other minor change to note: Instead of earning 2 Diners Club Rewards points per dollar spent, earning will change to 1 point — but Diners Club assures that the number of points required for redemptions will drop in half, so that awards will not become more expensive. Existing Club Rewards balances will be cut by 50% as well as part of this change.