Smart and collaborative people, usually a good work-life balance
Maintaining a strong work-life balance can be difficult when focused on business development and proposal efforts. Parental leave is fine but could be much better.
Mitre provides lots of opportunities for growth in technical tracks and leadership tracks. Because Notre is an FFRDC, there is always more challenging work than resources which creates a demand for... motivated people. Mitre offers many ways to continue growing allowing individuals to follow the path of paths they find most interesting. Great retirement plan. Many people that spend their careers with Mitre retire early.
Pay scale may be less than comparable work at "for profit" corporations.