Pros
The benefits. They are very generous with their dental plan and fairly so with their education reimbursement. My manager was also quite flexible with giving time off when requested. However, she was more of the exception than the norm. Because of the size of the company, you get to meet a lot of people and network.
Cons
It is a very large company and it is very easy to "get lost in the system". This often means that it is possible to be passed over for promotions and advancement. They do not hesitate to lay off their employees either. Often employees hear through the media before they are told by their management. Even managers who have been with the company for 20+ years are laid off without notice. It may just be the culture.