Pros
Tradition/Heritage, Job Security (all Government contracts now), Pay. Great place to gain experience, learn consulting/contracts biz. If you have a good project and a good manager, you will have a great experience. Company tries to have high standards, ethics, etc. Very organized. If you don't mind Dilbert gray-cubicle hell, conform, and do what you are told, you'll enjoy. Very structured.
Cons
Growing so large, you can get lost in the shuffle. To save money, they are sending more and more employees to work "on site" client-side. You get disconnected from the hive, the culture. I didn't get to know other associates/consultants. Management is more concerned about filling positions/contracts than people. They follow the money and hire just about anyone to fill the contract. As others have posted, becoming more contract, "fill a seat" work than true consultant. Since private side gone, all government. My experience was military. If they want your opinion, they'll tell you it. Not consulting. My manager rarely visited the client, did not provide project mgt. We were left to fend for selves, yet not empowered to create necessary change. Heard great stories about McLean and "back East". Seemed my location had developed its own culture and style.