Pros: Great benefits and excellent work life balance. Work with very smart and educated colleagues. Incredible flexibility with your schedule (though it depends on your manager, it is part of the culture)
Cons: I've been at MITRE for over 7 years, and things have changed dramatically since the Board appointed our current CEO, who most people I know do not respect nor like, which is unfortunate. It's very difficult at MITRE if you're not a systems engineer - you have to constantly prove your value and it's tough to speak their language. Additionally, it's a very horizontal organization that has a nepotistic streak in the culture, so it's quite hard to get promoted unless you have an 'in' with leadership.