Pros
As a non-profit, the AAMC generally operates on a 35 hour work week so it's easy to achieve a work-life balance. There will be a few hectic times of year with long hours usually leading up to or during big meetings or events. People are generally friendly and easy to work with, and there are many passionate employees that want to positively impact academic medicine and healthcare.
Cons
The association can be rather silo'd and you may not get much exposure to parts of the company you're interested in unless you really hunt them down. There are a lot of long-term employees (10-20 years), especially manager roles, that are great for institutional memory, but not always great for innovation and exploring new ways of doing things. Younger employees tend to stay only 2-3 years as there aren't that many opportunities for growth or advancement in many departments.