Pros
Very interesting work and projects. Offers a very fair balance of work and personal time. Offers the ability to move around and work in different engineering career paths and different business areas, along with different types of final products. Pay is very comfortable and benefits seem good.
Kontras
Most jokes about working as a military contractor are true, such as the "90/10 rule" where "10% of the employees do 90% of the work". There is also a good sized population of senior employees that seem to be content with "coasting" the rest of their career. Career advancement criteria is hard to quantify, so the "rankings and rating system" used is close to a popularity contest, but if you are known to produce results and a "team player" (and you have a strong vocal advocate as your section/dept lead), you can fare well over time.