Pros
It is possible to work on very rewarding technically challenging projects from time to time. The flexibility of the "work life" arrangement is superb, better than anywhere. MITRE offers flexible work hours and to work from home. The benefits package is better than most. There are some very talented scientist and engineers to learn from and they are genuinely good people. MITRE work has direct and positive impact on our society. That is very rare indeed. MITRE can be great. A company that is truly "non-for-profit and works in the interest of the public" is sorely needed in today's society.
Cons
MITRE has become yet another government bureaucracy burdened by both government procedures and there own internal procedures. It is no longer the "think tank" or the "research center" it once was in its glory days. Productivity and innovation are now being replaced by buzzwords and politics. There are tens of families employed by MITRE and career development is heavily influenced by this. Since there is no real line between management and engineering (causing both to suffer); management appears to take the credit for their engineers ideas and hard work. Knowledge sharing is limited as a result. Research opportunities have been limited as late and are not as forward looking as they should be. Arguably, the same individuals obtain the majority of research funding. MITRE should promote innovation by enabling many smaller research initiatives and allowing the real innovation to flower. Currently, innovation is squelched by those promoting there own interests. A whole new innovation program was formed to address this; but it fell short in execution due to the fact that those running the new program were the problem with the old. This is an example of mingling management and engineering.