Pros
High pay for the industry. The lack of a union might seem like a bad thing, but fed ex pays more than UPS (which has a union) and you don't have to pay union dues to work there (amounts to hundreds of dollars).
Cons
Hot, brutal, physical work. I didn't really mind it, but there is almost no support such as ladders to reach high packages. Working like this for years might permanently disable you. The real expectations of the job are that you can lift 150 pound packages unassisted from below your feet (down in the belly of a truck). Very dangerous environment too, I would wear my glasses (the amount of dust in the air made contacts uncomfortable) and during my 2.5 months there I was hit in the head by boxes badly enough that it bent my glasses probably a half-dozen times. I also had a friend knocked out by a falling box, I was hit in the back by an entire wall of collapsing boxes, and on multiple occasions I nearly broke my toes with falling boxes (remember to buy steel-toed boots).