Ventajas
Lockheed Martin, being such a large company, has hundreds if not thousands of contracts. Most employees have opportunities to work on a large variety of programs over time. The company has a strong focus on ethics and it shows. They pay 100% of tuition for related degrees (as long as you give them a year after your latest course.)
Desventajas
If you want to move up the ladder, the only track is toward management; Only rarely can one stay on a purely technical route. Merit increases are counter-active. If you're rated as highly successful, but you're close to the top of your salary range, you might get 1%. If you're average, but are on the low end of your salary range, you could get as high as the merit budget (usually 2.5-3%). Furthermore, because ratings are tied to the budget, they're rationed out on a bell-curve. Not all high performers can get the rating they deserve. This provides no incentive to do better. Human Resources controls your career, not your direct managers. If you want a promotion, your managers and higher-level directors have to, literally, fight for you. Yes, literally.