Your experience will greatly depend on which contract you're supporting. Some people will have it better, others will have it worse. One thing that is consistent is NO UPWARD movement in terms of dollars. There is a hard limit on the maximum raise you can get (and it's very, very small). So if you're looking to become a Senior, Director, or Management (Positions that pay $300k+ at a private corporation), then you're going to be doing it for FREE! You typically get the salary you signed and don't move from there (unless you're sleeping with the boss?).
Essentially, this company is good if you need a place to chill for a few years, as they primarily focus on meeting the minimum contract requirements. This means that work won't be too difficult (unless you work in proposals). However, the pay is FAR BELOW the same jobs at a private corporation.
CAUTION: If you think you are being offered a good salary, make sure to double-check the BENEFIT PACKAGE. They have multiple options, and even the best one is EXTREMELY EXPENSIVE! Think 15k+ in potential medical expenses...
CAUTION: They use a NORMAL DISTRIBUTION to evaluate performance each year (like many evil corporations). This method compares employees to each other, and whoever is best at lying or stealing other people's work will get a raise!
WARNING: Leidos prioritizes seniority over qualifications. If you think you're going to come here and progress upwards, think again! People who have stayed in a specific job role for 10, 15, 20+ years will be prioritized for advancement even if they have no education, skills, or contribute any real value.