Pros
Respected company. Secure long term financial viability. Varied cross-platform opportunities. Much room for growth. Competitive salary and benefits package. Pleasant place to work. Very, very competent and highly skilled colleagues. If you work or have worked for Lockheed Martin, then it will always serve as a feather in your cap... opening doors down the line in your professional career.
Cons
Very large company -- slow to make rapid market shifts. Bureaucracy. Very long hours -- dilutes salary structure and undermines productivity and workforce synergy. Ultra-competitive environment. Family sometimes "needs" to take a back seat. Too large. Senior management jobs seem to be awarded for "time served" similar to prison. Weak mid tier management structure. Again... tooooo large. Not much room for "out of the box" thinking... very safe approach to design services.