I was a Store Standards employee at Wal-Mart. While it was a rewarding job, you work HARD. From carryouts to collecting carts, it is your responsibility to keep all cart bays under your jurisdiction at full capacity at all times. You are expected to prioritize carryouts and cart collection, but you also substitute for the maintenance crew should they be absent, as well as helping floor crews with whatever they need. Safety, speed, and efficiency are absolute essentials, as well as having a keen ear and excellent shoes. Be ready to be run off your feet doing carryouts with little room for cart collection and plenty of customer complaints on busy days, and creating make-work projects or asking your front-end manager or other crew members for projects on slow days.
As for Walmart themselves, I had little problems with them as far as work goes. I found that, as long as you try to keep a good attitude and are willing to work, you'll be fine. Otherwise, they'll be on you like a sweaty shirt on a summer day. They mean well, though, so take it with a grain of salt.