We have two Walmarts in town; one is fairly clean but the other looks more run down. I think the location has a lot to do with it.... The north location is located in a more middle to upper class residential area whereas the south location is located closer to the lower class housing. Thus the north location tends to be cleaner, and the people (both workers and shoppers) tend to be less "exotic". We also have a K-Mart that is in the center of town and closest to the lower class housing, and hence tends to be in worse shape than either of the Walmarts.
I do have to say that the customer service is probably lacking at Walmart vs. our main grocery chain. Hy-Vee (our grocery stores) have as their slogan "A Helpful Smile in Every Aisle" which just goes to show the length they go through to establish good customer service. The workers at Hy-Vee are very knowledgeable, esp. in the department they are working in; for example, workers in produce will be able to direct you to the starfruit and even some of the produce managers can help you tell which starfruit are in the best quality, how to prepare them, etc. And if they do not know, they don't try to guess, but will rather try to find someone that knows the answer to your question. Hy-Vee also boasts having chefs and dieticians on staff, which are great resources for advice on different foods and how to prepare them. Their prices may be a little higher than Walmart (esp. for national branded items), but then their quality of produce, the better customer service, and greater selection (ie I think only Hy-Vee carries startfruit; the Walmart produce worker would probably just look at you like you had sprouted horns!) are well worth the extra cost. If I need to pick something up quick, or am buying a lot of cleaning agents from national brands, then I'll head to Walmart (they are the closest store to my house), but if I'm on a large grocery trip or need some advise from a professional chef / dietician I'll go to Hy-Vee instead.