(MONEY Magazine) – Since our November roundup of cashback credit cards, American Express has rolled out its own model. Our verdict? The new no-fee Cash Back Card from American Express (800-942-2639) is a top choice for anyone who charges more than $3,000 a month. Both the standard and platinum versions pay 0.25% on the first $2,000 charged for the year, 0.5% on the next $3,000 and 1.5% on purchases over $5,000. And there's no annual cap on rewards. That gives AmEx the edge over Discover's Private Issue, which pays a top rebate of 2% after you spend $12,000 but cuts off the cash flow after your annual charges reach $32,000. (Discover, by the way, is challenging AmEx's use of the name "Cash Back.")

Lighter spenders are still better off with a card that lets you reach its highest rebate tier quickly. Our favorites: the GE Rewards MasterCard (800-437-3927), which pays 1% after you charge $2,000, and the First USA New York Life Visa (888-200-1716), which pays 1% after you spend just $500. Finally, this new AmEx lets you earn an extra 0.5% back if you carry a balance. But savvy cash hounds know that the 17.99% you'll pay in interest will eat up your rebates. --SARAH ROSE

WATCH OUT FOR HIGHER INTEREST RATES

If you've picked a credit card from our monthly list of low-rate offers (see below), you could be in for a rude surprise. One of our low-rate mainstays, Huntington National Bank of Columbus, Ohio, sold more than 40,000 accounts to Metris Cos. in St. Louis Park, Minn. last summer. Soon after, some of those cardholders learned that Metris (which also does business under the name of Direct Merchants Bank) was raising their interest rate. Although Metris will not say what rate it's charging all former Huntington clients, one cardholder told us that her rate jumped from 9.5% to 12.9% in November. If this happens to you, try for another low-rate card.

The lesson for every credit-card holder is to keep a close eye on the mail. Even your original bank can change rates and fees simply by giving you 15 days' written notice. "These programs can be pulled at any time," says Robert McKinley, publisher of the credit-card newsletter CardTrak. "If you have a low rate, make sure you're using it to pay off your balance." --Jean Sherman Chatzky