Pros
Great opportunities to advance. I've been a package handler for about a year now and am now about to advance to a full time administrative associate position with full benefits. Awesome hours if you're a student. At my terminal, there's two shifts for package handlers: inbound(3am - 7am) or outbound(5pm -9pm) leaving plenty of time for any other daily activities you may have. It's like a paid workout. I've lost so much weight working as a package handler, and I've gained a lot of muscle mass. It's nice knowing that I'm getting paid to improve my strength. If you're a hard worker, you will receive recognition through quality recognition points(which you can redeem for nifty hooded sweatshirts or hats or whatever) and employee of the month awards.
Cons
Some managers are pretty lazy and useless. I've only had one manager that I really respect for the amount of effort they apply to their position. It does get REALLY hot and REALLY COLD in the terminal. I've come close to passing out while loading trucks before in the summer. They do provide juice/water on these hot days, but still, it's flippin hot. The terminal I was at before I transferred to my current one actually would not turn on the heat in the winter, so it was freakishly cold in the winter, and you couple that with sweating and it's just uncomfortable. High turnover rate. If you're working at a bigger terminal, be prepared to see alot of people just walking out or quitting randomly, and leaving alot of slack for you to pick up. My advice for this situation is, just keep your mouth shut, stay optimistic, and just do the work. You'll receive recognition better this way.