I do have the Target card & get the 5% off. It's a sweet deal.

But - with the Costco card - we do get a percentage off using their AMEX card. But I also get a percentage off on my Chase Visa & sometimes it's 5% on groceries, etc. So it's almost a wash. Plus there is the hassle factor. A Costco run can eat up a big portion of an afternoon, since I don't go in for just one thing.