Pros
Lockheed Martin IS&GS, per my reckoning, is the less attractive, but stable side of the company. The contracts can be fun and the projects are big. I have met many people who I felt would be great mentors as I've hopped across projects.
Cons
The bureaucratic machine of IS&GS is woefully painful and lacks strong leadership. Middle management, on at least two projects,showed lack of direction that lead to delays in delivery, performance and, ultimately, loss of business. Working at a "customer site" can lead to loss of identity for on-site employees. The ability to move up within the company is subject to the performance of the contract as well as your mobility to move to other LMCO projects. I loved the work I did, I hated the games and string-along management did and it was ultimately the reason I left.