Diners Club, which I highly recommend, has had one major drawback: acceptance.

You can (and should) rent cars with it, pay airlines and hotels, and buy electronics from several major chains. But you’ve just never been able to pay the local drycleaner with the card.

But that drawback is going away. Diners Club and Mastercard have signed a pact so that beginning in November Diners Club cards will be accepted anywhere that takes Mastercard.

I’m not sure how this is going to play out. Assuming the Diners Club Rewards program remains in tact, this will be the ultimate credit card — arguably the best rewards program (I personally go back and forth between it and Starwood) combined with worldwide acceptance. However, the reason that acceptance has been low is that Diners Club charges higher interchange fees than other cards. So merchants are loathe to pay the costs of taking the card. If accepting Diners Club as a Mastercard implies lower interchange fees, Diners Club could be expected to cut costs of their reward program. So we’ll wait and see how this develops – but it could be huge.