Pros
Varied and interesting work, frequent opportunities to tackle problems outside your usual experience. Management and staff are nicer people compared to most private sector engineering companies I've worked at. Very flexible work hours, good benefits, layoffs almost never happen, laid-back atmosphere if you want that.
Cons
Some departments get lots of promotions, others little or none. MITRE doesnt tell the staff which technical specialties they value, you have to figure that out after a few years there, but it makes a huge difference in raises and promotions. They seem to really like systems-oriented expertise. As consultants, MITRE is expected to be expert in anything the Govt. wants help with, so they throw whoever needs coverage in their department at the problem, sometimes someone who doesnt really know what they are doing on that problem although they may think they do. There is an assumption that anyone from MITRE can be an expert in anything the Govt. needs advice with, resulting in good or bad advice at various times. Department management #1 priority is keeping their own people at work, which sometimes limits using expertise in other departments. Review process (P&D) is a joke to deparment management. MITRE's main product is viewgraphs to advise Govt. MITRE projects usually dont really need to make anything actually work all they way since MITRE doesn't actually field systems, only prototypes at most, but thats a problem not only at MITRE but in lots of Govt. high-tech systems since making promises they can't deliver is often the only way to get the Govt. contract in private industry. MITRE is supposed to help with that, but the DoD is so politicized that it can be impossible, and if you say 'this won't work' on a huge program its like saying 'the emperor has no clothes' and its not appreciated and not listened to by the DoD decision makers and sometimes by MITRE project management.