Pros
Many opportunities to move horizontally or vertically in the company - preference to hire internally. Professional, respectful, yet comfortable company culture. Excellent company benefits. Incredible managers that help you do your best work while keeping a healthy balance. Management proactively invests into your skills/career development. Once you are in, they want to keep you and invest into you, you have job security.
Cons
The work can often be uninteresting or feel disconnected, since you are a small part of a greater whole. Your unit may have a very traditional background and be behind the latest technologies. The salary can stagnate and fall below market rate with longer tenure.