Pros
You will probably get the chance to work with some very intelligent people and get involved in some interesting projects. The actual work isn't the bad part of the company. They do their best to support their workers, sometimes not able to (see Cons below). Good for a mid-career employee and those who knows what track they want to be on for a while/rest of career.
Cons
Each little division in SAIC has it's own budget for everything. They can not support an employee interested in another competency area of the company. Their training budget is woefully underfunded and very narrowly applied to what is in each division's best interest. Not a good company for an entry level employee or those who aren't sure of career path. I say this because if you want to change from your current job to another field that SAIC specializes in (and even one that has huge growth) they have no system to say "Hey, this is a good employee we should support them and hire them in this division". Maybe I'm just hoping for too much.