Pros
The best reason is the compensation and the tax advantages of overseas pay, the ability to travel worldwide and learn about other countries. Working overseas with KBR or any other government contractor is a very challenging experience and not for the faint of heart. KBR is actually one of the more organized companies overseas and make good efforts at ensuring your paid ontime and have a decent benefits package. Other contractors largely leave the employee on their own to figure out things like passports, visas, payroll problems, etc. KBR takes care of its people.
Cons
Much of government contracting, especially in the middle east is ate up with lots of retired military types. These retired military types do not know how to manage people in a civilian environment and act as if they are still active duty. If you were prior military at one point in time, dont disclose your rank, because if you were lower rank than they were, they will treat you as a subordinate. Also, working overseas in the field, you have a great variation in the quality of the housing. It can range from living in tents to living in a furnished apartment. If your willing to live sparsely and simple, then you wont have a problem.