Pros
As a young engineer, I've found the work to be very interesting and challenging. Great opportunities to learn about engineering and complex systems - not just from the work but also from the myriad of subject-matter-experts available. If jets, missiles, lasers, and spacey things are your bag, I expect you are not likely to find a better place to learn. The leadership locally and at higher levels has been friendly, competent, and sensitive to employee concerns (at least in my experience). Every year there is a survey to gauge the health/happiness of the corporation and all leaders seem to take it very seriously.
Cons
I expect the compensation and perks will never quite match those of other leading high technology firms since we're working primarily on the government's (taxpayer's) dollar and perhaps rightfully so. Similarly, being government work and all, it comes with a lot of soul-crushing and often hilarious bureaucracy and red tape as you might expect. Audits, reviews, reviews of reviews, meetings about meetings, and so forth are all commonplace. Every 6 minutes of your time has to be accounted for when filling out your time card.