Pros
If you are open to it and it's something you really want, you can learn a lot about how a business works and it is possible to learn and develop skills. I worked at Walmart while earning my degree and my managers were supportive of that goal and willing to let me change my availability so I could go to classes. Once you're off the clock you don't have to deal with anything and can go home without bringing work with you.
Cons
You will always have to give more to Walmart than you will get in return (especially compensation-wise). Workloads are heavy. Customers can be nasty and will treat associates poorly. Many long-time associates like to compare the way things are now to back when Sam Walton was running the company and say things have gotten worse.