Pros
Decent pay and decent benefits. If you want stability, this is the company for you. You'll be doing government contracting, which is often very laid-back. It is very easy to blend into the background here.
Cons
It's very easy to wind up on a terrible project. If you aren't careful, you will quickly find yourself stagnating as a developer. All of the new people that come to my project are desperate new college graduates without other options. To be fair though, that's what I was when I got here. They seem to have a hard time holding on to good mid-level talent. Company culture is non-existent since most of the time you'll be working at a customer site (a government facility). There will be other SAIC employees there, but it's still a government facility and you'll be a government employee in all but name. These downsides aren't specific to SAIC, but are typical of the downsides generally found in defense contracting. SAIC is a defense contractor though, so most of them apply. Bottom line: If you don't want just ANY job, then seriously consider the points above.