Pros
The compensation was fantastic and benefits were good in terms of tuition, retirement, and health. You have to really take control of your own career and (obviously) work hard, continue to learn in your discipline, and network with others. You will have opportunity to work on very very interesting projects. Additionally, if you get involved with pursuit of research contracts and earn a few wins over time, you will be held in very high regard and asked to participate in a number of projects as people get to know that you do excellent work. This takes tremendous sustained effort, but, then again, anything worth doing in life is worth working hard to achieve.
Cons
very very process laden environment which I suppose is necessary for such a large organization to function effectively . There are a handful of less productive people who are very well socially connected and seem to advance because of this. Incentive to younger workers should be pursued. Younger workers leave after a few years 3-5.