Pros
I have been with LM for over three years, they have always been fair. I started as an engineer and am now part of management. The business unit I work for is like working for a smaller company, they are nimble but have the backing of the Lockheed Martin. The salary's a above average and the benefits are fantastic. Because of economies of scale, my health insurance premiums were cut in half between last year and this year. The ability to move up in the company is there, but you have to work for it. They promote deserving people and reward success.
Cons
You have to be prepared for the work-load. At times working 50-60 hours a week is necessary, but at other times the schedule is flexible. Also, being a defense contractor (even though they do ALOT of space work for other government, Non DOD agencies) can be difficult. You are at the mercy of the government, if there are cut-backs there can be some scrambling to ensure people remain gainfully employed. Another issue is obtaining new business, they are very good at identifying opportunities, but then the follow-through is not always there. My team has identified business in different areas that would be a good fit, but sometimes it goes nowhere when it is pushed up the chain. At my level of program management, I don't always have the time to chase the work when I have to focus on my customer 100% of time.