Pros
Very generous benefits package to the point it makes salary alone almost an unfair comparison. I believe every 20+ Milliman consultant would be considered "on track" for retirement by any financial adviser. Their profit sharing and retirement plan match makes it nearly impossible to not be prepared. Health and other benefits are also outstanding.
Cons
There is no set career growth; it is what you identify and create for yourself. It is a very flat organization. Career growth is measured in skills opportunities not leveling up and job titles. There is a bias rewarding actuarial exams and other industry-based designations more than technical, human resources certifications. Milliman leadership provides the normal "thanks" but little more in showing appreciation for what you do. Going above and beyond is the norm so recognition for it is rare. It is important to self-promote and generate your own appreciation of your contribution to the firm and your career growth. Know when you are doing a good job whether managers acknowledge it or not.