Pros
If you are competent and you work in the backroom you will quickly be exposed to all aspects of the backroom. The pay is good compared to fast food or most other retail, but not career oriented jobs. The jobs are simple, which allows for a good mindless labor to act as a break from the academic stresses of college. The duties are varied enough that it doesn't get overly boring or repetitive if you're working as a material handler or a donation attendant. Also, you frequently come across really cool and interesting donations as well as donators.
Cons
If you are competent and work in the backroom, specifically as a material handler or a donation attendant, you will quickly accumulate tasks that you're expected to do, which will get to be very overwhelming during busy times. Also, there's a lot of turnover with employees that aren't very competent, which results with you picking up the slack for the people who are gone, didn't do the job right, or don't know what they're doing yet. The job doesn't really advance much and unless you're very lucky full-time work doesn't happen.