Pros
There is a lot of job security working for a government contractor. Once you are hired, it seems virtually impossible to lose your job. If you like to sleep at work, this is a great place.
Cons
As a software development company, GD is terrible. The process for developing software is very far behind the industry standards. Process is much more important than getting anything actually done. It doesn't matter how hard you try to be successful and work hard, you are always pushed to be a mediocre contributor. At GD you will simply be another warm body which they will constantly push you towards being just average. They will constantly pitch flexible work hours and great people, however, the hours only flex upwards, often demanding at least 48 hours of work. The amount of hours you work is MUCH more important than the amount of work you complete. If you slept for 30 hours a week and did 20 hours of work, you would be valued more than if you worked 40 hours straight.