I love Costco and the cash back is great, I always get at least $100 dollars and I pretty much use it for gas and when I shop at Costco since these are where you get the most cash back and their gas is the cheapest in town anyway. The interest rate, however is really high and my spending limit is low which I thought was due to my credit rating when I got the card (I was in college and didn't have much credit established at all), but I've asked for my credit to be reviewed now that they're around 690 and I still have only a $500 limit with a 27% interest rate! I used to pay off my card twice a month or so, but since this was annoying, I switched to using my Mastercard for everything except Costco and gas. I love the rewards, but I hate having to check my balance on my card carefully every time I use it because the limit is so low I don't want to go through the embarrassment of getting denied.

I really like this card, as of 2010 it provides cash back for gas (up to $3,000 sales per year) and restaurants @ 3% and travel @ 2%; everything else (including gas after $3k in sales) gets cash back @ 1%. The reason I'm with a cash back card is because I found a lot of the other rewards cards (like my BoA Visa Signature) provide points at around 1% of sales but the cost of the services you can use those points against are noticeably higher than what you could get online or through wholesalers. My TrueRewards card is averaging almost 1.5% in cash back for me so far this year (with 2 months left) and I can pick whatever retailer I wish to acquire services from, which factors into the card benefits since I'm not forced to buy overpriced stuff from specific vendors to use my points. There are some things that I would like to have available in this card (like airline/hotel upgrades) but I guess I'll have to get a platinum card for those mostly travel-related benefits (though the lack of free domestic US companion airfare tickets now is a bummer).

Costco members will benefit from this card the most since it's both a credit card and a membership card. It has no cap on cash rebates and to my knowledge it is not tiered like other Amex cash rebate cards.

This card has one of the best cash back programs available. 3% for eating out, 2% for traveling, 1% everywhere else, including at Costco. The other Costco card and the Blue Cash are Tiered, so you need to spend a lot. TrueEarnings has no cap and the cash rewards are from the first dollar. This card and a good cash back Visa/MC make the perfect combo.