Pros
Top notch administrative support, facilities, resources, security, etc. Administrative functions treat you like you are important and care about how they take care of you. Very very rare. Almost no dead weight among the staff. Yes, some may underachieve but almost no dullards or phonies exist (almost is the key word). Virtually every one can lead or drive a project and is very intelligent. Most of what we work on is new and challenging. Most of us are very proud of MITRE.
Cons
Over collaboration. Large, diverse, teams collaborate real time to shape critical deliverables and whomever has the most political power gets final say for better or worse, even if they are not the subject matter experts. All the highly intelligent PhDs think they can read a couple of books and then speak knowledgeably about disciplines that they have little experience in. They do a pretty remarkable job but it would be better if they stayed in their swim lane. Many are inhibited and insecure. Some task leads think they know better and they don't. You have to play ball with them and the result is sub-optimal solutions. Some people guard their knowledge and work. I have seen some blatant plagiarism. Some take it for granted what they have.