Pros
The company generally tries to take care of their people. The pay is typically pretty good, the benefits are excellent if a bit expensive. Top tier insurance typically cost about $250 per check and caps at $5,000 max yearly out of pocket with $10 co-pays. They have a matching 401K program up to 6% (I think) and there are jobs all over the world.
Cons
Some PMs are better than others. Upper management has a habit of promoting lower level managers (with little or no training) into senior management roles. This creates a sink or swim mentality. They often then fail to hire a replacement manager at the lower level which creates a work vacuum for all personnel down the chain. When your contract ends they will place you in their career assistance program, which basically does nothing. If your task ends you have to go find a new jobs, even internally. Years ago they were better at this, but now the recruiters are just kinda blah.... College reimbursement is listed on all tasks but is only covered if it was included in the specific contract, if this is important then ask during the interview and get it in writing. Getting moved into a new clearance level is re-tardily difficult. GDIT will pay for the clearance but will not generally do the leg work required to get you moved into the role after the clearance is issued.