I usually look for Shultz on sale and grab a big bag when I need true potting soil. I personally stay away from anything that has fertilizers or moistening agents in them - e.g. Scotts. I like to control both of these things myself. If you want your soil to be a bit more moisture retentive, add some coir. For fertility, I use a general purpose fertilizer.
I have never bought potting soil at Walmart, but I do buy a lot of top soil, humus, manure etc from them.
