Pros
1. Great colleagues - Incredible wealth of knowledge and experience available from people willing to help. 2. Very satisfying work - Vast variety of projects and types of work with emphasis on best solving the right problem, not the most profitable (been there, done that - there is a difference). 3. Fantastic work/personal balance. 4. Justifiably in Fortune's Top 100 Places to Work for 9 years - Good at lots of stuff that counts.
Cons
1. Not for fresh-outs or newbies (unless you have a PhD, want to do research, and chose MITRE over a college) - Get some real-world experience to temper your learning: flame some electronics, choke some computers, and watch a contract grind down in dueling depositions. 2. Yeah, they have the occasional bad manager - The Peter Principle is, after all, a universal principle, and yeah, the lack of effectiveness rubs off on the underlings. Life goes on. 3. Recognition goes to the flashy demo - Not unlike the real world, but here it isn't temper by the facts of did it make money or not.