Pros
Highly rated ethical company, and I've certainly never seen an ethics issue. In addition, despite the conservative population that SAIC recruits (retired military in many cases), sexual orientation is listed specifically in the non-discrimination contract, and women are generally treated fairly, despite individual employees' issues that may or may not exist. SAIC is international in scope, and exists most places in the US. They're working on doing better at moving employees within SAIC rather than losing them, so even if you may move, opportunities may exist elsewhere in the company.
Cons
Each business unit is run separately (although corporate is trying to change that), and so there are variations across business units. My unit depends on relatively short-term government contracts, so there's not always consistency for what you'll be working on from year to year. On the other hand, I have a wide enough variety of skills that I can shift pretty easily among projects. I don't recommend SAIC if you want to do the same thing forever and forever.