Pros
Excellent mission, subject material far more interesting than anything in the private sector, prestige of working for the top DoD intel agency. Free educational opportunities, making a difference in national security. Don't want to work anywhere else.
Cons
I worked as an analyst for a while and went to a position to do operations support, thinking it would be more interesting. It was a total bait and switch. Instead of doing operations support, I became a glorified secretary and data herder; counting beans on spreadsheets, arguing with people about meeting task deadlines, and doing administrative work for leadership with very little guidance and no training. I desperately tried to escape back to analysis where I felt like I did more actual counterintelligence work. I was successful but can't leave soon because of archaic HR rules.