Pros
You get to work on projects that have consequence and meaning. Your peers and your bosses are all driven by the need to accomplish something great. Most likely, they are type As just like you and have the same passion for detail. As a result, the feeling that you get from being in such exclusive company is a source of professional pride. You also learn new skills from being on different projects across the world and interacting with experts in all fields.
Kontras
You sell your life to the company. The expectation is that you will work all hours and will travel at a moments notice. The management views its people as all replaceable, and they see you as expendable. The obsession with cost is also tiring, and makes it difficult to develop good supplier relationships.