Pros
Their benefits package was fantastic when I worked for the company (although I've heard their current options of health insurance plans are horrible). The physical work environment is fantastic - nice offices, stocked kitchens, in-house deli, exercise equipment and showers. Company-provided desktop/laptop computers are top-notch and are upgraded at least every 2 years.
Cons
I was extremely happy at SAIC for almost 15 years, but the company seems to be moving in the wrong direction today. Service Centers (HR, AR, AP, etc.) are replacing many positions within the line organizations and employees who have been with the company the longest are being laid off. I understand that service centers make good business sense in many ways, but SAIC is taking it too far. They used to care about their employees. Current employees laid off due to the new service centers are not being hired to work in the service centers. I assume that's because they can hire people with little or no experience off the street dirt cheap.