Pros
It provides a good experience, you get to work for a really great variety of companies, both large and small, as well as independent clients.
Cons
Where to start: depending on what store you get into, your boss[es] might be helicopter bosses, you can't sneeze without them asking what you're doing. No privacy, some owners watch you from security cameras and call to ask who called etc. You're expected to do things [such as shipping] without training. Sometimes asked to work off-shift without pay, including evenings and weekends. If your bosses are stingy with money, they'll inflate prices astronomically and force you to deal with customers if they complain about money. Uniform? Forget about it. Took 2 years to get 5 short-sleeved shirts [in Canada] and the long sleeve shirts are "coming". If a machine breaks down, you best hope you can macgyver your way into fixing it, because they won't pay for a technician to come fix it. Oh and, if you're swamped with work, better learn to duplicate yourself. You generally have to do everything yourself, owners don't help, and if you can't finish it because the time-space continuum exists, you better be prepared to explain yourself. And the cherry on top: if the owners are having a bad day, take cover. You will feel their wrath, physically and emotionally. The list goes on: basically amounts to - if you're just starting out and want the experience, great, but don't hold your breath to be treated with respect.