Central Market is sort of a superdupermarket — in size, at least. It's a division of H.E.B. so it has massive corporate buying power behind it, which keeps prices reasonable, at least for some items.
Having lived in places that have much better health-oriented supermarkets, i'm not all that impressed with Central Market, but it is a good complement to what one can find at Sunflower and Trader Joe's, and it's cheaper than Whole Foods for the most part.
There's a decent selection of organic and vegan items, though one has to look around to find them (tip: watch for the green price labels on the shelves, which are often — though not always — placed to help you identify organic items).
Chocolate fans take note: there's an uncommonly good selection here of organic, vegan, fair-trade chocolate bars, including some brands one doesn't see just everywhere. Just be sure to read labels carefully, as always. :-)
Cons: Sells meat and lots of crap, too, Can get extremely busy