Pros
Foundational research at the two core campus sites in actual technical specialties can be great work as you are a hands-on technical researcher and really contributing newly or can create new software rapidly. For several years, the company has been trying to change the entrenched culture by implementing "modern HR and structured management approaches". Financial and Health benefits are great. (rest isn't really useful or available due to little funding) Internal access to any topic and online training is excellent (if you have time to use it)
Cons
Government clients rarely get the promised benefit of independent public service perspective which is a FFRDC's charter, but rather, get MITRE's view of the world agenda pushed on them without real practical expertise solutions or a proper customer roadmap or a true partnership to influence the real government change that is asked for. Don't let the reputation of the company fool you or the best places to work surveys. It is highly driven by management that have no other experience but from within the company. Openness to really listening to the deep experience of those great people hired is not accepted. Best people are hired, best people leave when they see the inside. Your only chance is to get cushy with those who control project money and speak what they want to hear. The gossipy old boys club can have a email spread across the company in 60 minutes without any investigation into validity. Do not trust the company to take care of you for doing good work, your ideas are the companies here and you will not personally get advancement or credit unless you play the game. Do not work in remote offices unless you are ready to continually fight for reputation and projects to keep you funded. Remote offices that are customer facing and high stress have to fight the main company to get qualified experts to support projects vs. just supplying charge numbers for those not covered. No advancement in remote offices. Advancement of the non-qualified or poor people managers is frequent across the company. Independent ownership of tasks not encouraged or rewarded.