Pros
You will never get fired unless you start costing the company money and the benefits are pretty decent. Hopefully you know someone in senior management or in the family as they will create a job and pay you whatever salary you would like. Lots of lifers which builds a lot of tribal knowledge so once you learn something it costs too much time and effort to replace you.
Cons
Your job will change at the whim of upper management and they will tell you anything you want hear in order to fill a job vacancy. High turnover in some departments and it makes for a difficult situation when looking for career development. Get ready to have the finger pointed at you by management on anything and everything that goes wrong. If a manager gets the wrong idea about you it will spread throughout the organization and will end up getting you "blackballed" from moving up in the company and you will eventually be put out to pasture.