Pros
Job Security, exposure to cutting edge technology. Decent leadership is generally on your side.
Cons
They do not pay competitively to retain talent. basically once you have a security clearance at the top secret level, they know you'll want to tend to keep it and not just give it up by leaving. So if you're in a state without a lot of competition for defense work/cleared professionals, they know they've got you right where they want you and promotion and competitive pay is not going to happen without bouncing around in the company. While that is allowed, it's a pain with HR taking MONTHS for anything to happen. Also, you're at the mercy of government funding and I've been burned so far with every program being cut unexpectedly and you're stuck looking for a place to land. While they generally won't lay off when times are good, this is bound to catch up with you when defense spending slows down. Oh and health care is atrocious. 12k max out of pocket is too much.