Pros
Management recognizes hard work (at least at the Sort Center where I worked). There is no room for micromanagement, since each Area Manager has so many employees to supervise; they just look at overall progress instead of zoning in on individuals (though occasionally you will be audited - a standard procedure). The benefits were AMAZING for a part time job - I had medical, dental, and vision insurance, an employee discount, and countless other perks. The work was simple, though physically taxing, but nothing too bad. A free workout. If the managers see you working hard, they will reward you by asking you to do certain projects for them, or training you for light work in other departments, or making you a line-lead. Predictable shifts (you have the same, unchanging schedule every week). Also, very generous paid time off/vacation options. I took about a day or two off every month and a short vacation every other month.
Cons
I received a seasonal promotion and worked in another department for the holidays, and the specialists who supervised me during that season treated me (and some of the other seasonals) like cr@p. Lots of lazy people working on the lines, who don't care to see things get done. It could be the busiest, most high volume day ever, and they will still feel no sense of urgency. There were never enough good scanners for everyone to use, so people would have to fight for them. Overly bureaucratic. There are strict rules to follow regarding everything. Some of the Operations Managers were a little haughty and not very approachable. The area managers were very nice though. When you get injured at work and visit the on-site medical center, they WILL put you on blast and use you as a safety example the next day at "Stand-Up" (the meetings that occur before every shift where all employees are present and addressed by management). They will also make you do tons of paper work, no matter how small your injury is.