Pros
The work you do has a direct impact on the nation and its security. You feel good that you did more than "just earn a paycheck". You will work on things that people in the commercial world would never even think of. Great benefits, especially flextime and 9/80 weeks, flex time.
Cons
Very process intensive. Some of the processes are over the top. If you want to be promoted, learn the processes. It is actually more imponrtant to understand process rather than actually "know" how to do something. Development (R&D) is everything. Normal IT is not as valued. Some incompetent people should be let go. Putting up the government bureacracy can be very frustrating. You are at the whims of the congressional budget. The business politics often have the business units fighting with each other.