Pros
Good place to start out, get some experience; and move on.
Cons
I've seen people promoted to positions they did not deserve, while the person who puts in 100% gets passed over time and time again. I have been through three major "re-orgs," and had my title changed, pay changed, managers changed (three times in one year once), and have seen good people leave due to the overwhelming feeling of discouragement when they are passed up for a promotion yet again given to an incompetent person who "knows" someone. It is difficult to work like that everyday, and I can understand why people leave. It is also highly compartmentalized, which means that once you have worked there for a few years or more; it becomes difficult to be marketable to another company.