Vantaggi
I had a long career at SAIC-Leidos and overall, was appreciated, given challenges, and always felt my salary was good (in market range). They have a lot of top talent and solid processes, good diversity of work and client base. You can learn a lot from your colleagues here. Amazing people, lots of talent, "thought leaders" although that is a hackneyed phrase, they really have them here. For a self motivated, driven young professional this can be a good place to learn the skills that will last you a career.
Svantaggi
The company is in a transition time now; Leidos is a new company spun off from the former SAIC. Splitting SAIC into two companies -- Leidos and SAIC -- extended transition years that began in 2006 when the former SAIC went public, initiating a huge culture shift. This was a hard transition for many long time SAIC'ers who were used to being client-focused and felt the focus shift to numbers and making upper management happy and worrying about reporting numbers to "the street." The split which came years later (splitting SAIC into Leidos and SAIC) left a lot of the juicier, more expensive vertical work with Leidos and the lower-cost plug and play IT work with SAIC. At the time I left, I was seeing people being let go who had given their lives to the firm, and some others leaving either because they were unhappy with changes, or were being squeezed down and out and saw writing on the wall. If you work here, never forget that at any publicly traded company, they care about numbers. Don't be lulled into thinking someone will have your back, because even if your boss adores you and would go to the mat for you and your clients are happy, senior management can always come in and move the pawns around to meet some new top down edict or cost cutting initiative. Use your time here to your own benefit, you will definitely have smart people to learn from, but there is still some tumult there and probably will be for a while yet.