Ours here are nice and clean, stocked well, and usually the service is good.
The other night I was in line for a good 45 minutes. At first, I thought customers just had a large amount of items but after all that time, the reason for the wait became apparent. The cashier had no sense of speed, picking up one object, slowly moving it to the scanner, after it scans, pause, then SLOWLY move that item to the bag. Pause. SLOWLY reach for the next one, all one-handed, all in this slo-mo repetition... After a few minutes of this, I had all I could do not to yell at her to get the lead outta her asset and move faster. (And, no, she was not handicapped, not slow mentally... There was no reason for it.)
That is why I hate Walmart. I shop for the groceries more often than my wife because she works out of the home.
I refuse to go to Walmart because that has happened to me more than once. They will have 36 checkout lanes and only 8 staffed with one person. Typically there are 3-4 people waiting in each line. Also, Walmart is more expensive than my local grocery store chain Market Basket.
I have the same issue with Home Depot. Although there I am usually only buying a few items and I go to the self checkout. They tyically will only have one or two checkouts with an actual person.