Lost of opportunities within, lots of CBT training, great projects. Possibility of staying technical or climb up the ladder. If you within a project-oriented competency (developer, researcher, scientist, Q/A, PMP, etc) couldn't find a better place...
Cons
... But if you are like me, a maintenance-oriented professional (DBAs, network/sys admins), well, it feels like trying to fit a round peg in a square hole. Also, the ever present chance that your project is cancelled due to government cuts.