Not the cheapest place to buy staples like masa for tortillas, but a good place for foodies to pick up more specialty ingredients such as masa for tamales, epazote (a traditional herb that goes in beans, also has anti-flatulence properties) and huitlacoche (a fungus that grows on corn). Also, they have a wide variety of prepared foods for the less adventurous: I have also heard good things about the ceviche from friends.
The ladies who runs the place is very nice, and I was very happy with the customer service: I bought a tortilla press, which broke the first time I used it. When I returned to the store, she let me have another brand of press (much sturdier) for only the items' price difference of a few dollars.