Pros
UPS offers great benefits for part-time package handlers (Health, dental, 401k, discounted stock, tuition-reimbursement in some areas, etc). The starting pay sucks but raises are pretty frequent. I started at $8.50/hr almost three years ago, and am currently at $12.15. Job security is definitely another pro. After the first 30 days, it is nearly impossible to get fired unless you get caught stealing or no call-no show for three days in a row
Cons
At the hub I currently work at, part time package handlers usually start out as an unloader or loader. When working in these trailers, it is crazy hot in the summer months, and cold in the winter months. These positions have a very high turnover rate, but for some reason our hub attracts a lot of lazy workers. These people usually last a week or so, and quit, or complain to a PT supervisor and get moved to an easier position. Hard work is usually rewarded with harder work, since they have to pick up the slack for these lazier people.