Amazon Rewards Card promo. Source: Amazon.

Do you find yourself spending thousands of dollars per year on Amazon (AMZN -0.68%)? Are you a Prime subscriber who can't live without two-day shipping? Then you might be interested in the Amazon Rewards Card.

The credit card, backed by JPMorgan Chase, offers an aggressive rewards program that may be attractive to frequent Amazon shoppers. But does it make sense to sign up?

3% back on Amazon.com purchases
The single most intriguing aspect of the Amazon Rewards Card is the 3% back it offers on purchases at Amazon.com. If you spend $5,000 on Amazon.com in a given year, using the Rewards Card (in place of another credit or debit card) could save you $150 annually. That's the card's best attribute by far, but it's not completely useless otherwise: The Amazon Rewards Card also offers 2% back on purchases at gas stations, restaurants, and drug stores, as well as 1% back on all other purchases. There's no annual fee, so you won't pay just to keep the card open, and there are no caps on your potential rewards.

Some limitations to keep in mind
That said, there are some significant limitations and shortcomings with the Amazon Reward Card to keep in mind.

I can't stress this enough: Carrying a credit card balance may be the single worst personal finance decision any individual can make. Simply put, don't do it!

The interest rate on the Amazon Rewards Card is relatively high -- about 14.24% to 22.24% depending on your credit score (JP Morgan offers cards with lower interest rates), making it particularly onerous for anyone carrying a balance. There's also no special introductory offer -- many competing credit cards offer new customers 0% introductory rates for the first year or longer, but the Amazon Rewards Card does not offer balance transfer incentives like many other cards.

It also doesn't have the variety of perks some other credit cards offer. Some American Express cards, for example, in addition to giving cash back, offer cardholders free roadside assistance, early access to exclusive shows, members-only travel deals, travel assistance, extended warranties, and discounted deals on other online stores. There's nothing to stop you from having a wide variety of credit cards and using particular cards with particular vendors, but if you're looking to limit the number of credit cards you use, the Amazon Rewards Card may be one to skip.

There's also the psychological factor to consider: Amazon often has the best prices, but not always. There are some goods that can be found cheaper elsewhere. Yet, if you have the Amazon Rewards Card, you may be tempted to do less comparative shopping, going straight to Amazon every time you need to make a purchase.

There are other alternatives out there
What if you don't care about those things, and simply want to shop on Amazon? In that case, the Amazon Rewards Card looks like a much better deal, but there's still another card out there you should consider. Discover's It Card offers a rotating series of 5% cashback bonuses, one of which includes Amazon. The 5% bonus changes every three months, but during that three-month window (which begins in July this year), it offers 2% more than the Amazon Rewards Card on the exact same purchases.

Good for dedicated Amazon shoppers
With that said, the Amazon Rewards Card still makes sense for consistent, heavy, year-round Amazon shoppers: You will not find another card that consistently gives you 3% cashback on Amazon purchases. Just be sure you pay off your balance every month.