WalMart rated worst supermarket in U.S.

Anyone who's has had to navigate a shopping cart traffic jam or attempt to efficiently use a self-checkout machine knows that not all supermarket trips offer a stellar customer experience. But some are clearly worse than others.

Consumer Reports conducted a survey of more than 27,000 subscribers in its May issue and ranked the country's 55 largest grocery store chains. The results prove that bigger doesn't mean best. Wal-Mart (WMT) -- which is America's largest supermarket, with more than a third of all grocery sales -- landed on the bottom of the list: Of a possible 100-point score, the retail giant received 67.

At the other end of the list, the top-ranked supermarket was east-coast chain Wegmans, which received a score of 88 out of 100. Other top scorers included Trader Joe's (87), southern chain Publix, and Costco (COST) (84).

The survey also asked shoppers about their biggest gripes, and found insufficient open checkout aisles to be the most common complaint, cited by 19 percent of shoppers. Other issues included crowded aisles, out-of-stock advertised specials and lack of choice.

A third of those surveyed told the magazine they had switched grocery stores in the past year because of high prices, long waits, inadequate selection or poor food quality. Despite the gripes, Americans are still visiting stores, logging an average of 1.2 supermarket visits per week, according to the Food Marketing Institute.