Pros
The benefits are, by far, the best reason to work for UPS. There are very few employers out there that offer part-time employees such good benefits. Another benefit is that you know the hours you will be working everyday. The preload always runs Mon - Fri and you are almost always done with work by 9:30 AM. This allows you to be very flexible during the day if you desire to hold a second job, or attend classes. The job itself is not that difficult. Although, it does require tough skin sometimes to deal with the whining and complaining from preloaders with a poor work ethic or drivers who complain about the quality of their load.
Cons
The hours are one of the benefits, but one of the drawbacks as well. It is a hard adjustment for some people to get up at 3:00 AM to go to work. Also, starting pay is not that great. Oftentimes, preloaders that you supervise who have worked at UPS for several years will be making more than you. If you take a part-time management position with the hopes of getting promoted to full-time, well, good luck. UPS has always treated me well, but from the day I started I have been told that there are promotional opportunities. If you take the job for extra work, then that's great. If you want to make UPS a career, then seek out the positions that are full-time and apply for them directly. They need part-timers to run the day to day operations, so some managers don't really want to help people develop a career with UPS because then they would have to find someone to replace you.