Pros
Lockheed Martin offers a great amount of security and professional growth for a wide variety of career paths due to its size and reach - there are Lockheed Martin facilities in nearly every state and many other countries. Awesome benefits compared to other companies, especially when it comes to relocation to another LM unit. Ease of transfer as well - just find a place you want to live and odds are LM is there already.
Cons
The company is extremely large and tends to move slower than a startup, so if someone is seeking a fast-paced environment, they may not be pleased with this company. The company is also very "politically correct", due to lawsuits and fines, so creativity and the x-factor of workplace synergy can sometimes be stifled.