Pros
You'll work with wonderful people. The work-life balance is basically good (though it's not what it used to be; workloads and expectations have ratcheted up significantly). The mission is warm and fuzzy, and staff genuinely care about making life better for people 50+. Pay and benefits are quite good.
Cons
There are some key execs who have undue influence and are in the wrong roles based on their skill sets. There's a lot of infighting and dysfunction. But a lot of terrific people stay because they believe in the mission and they genuinely want to make the organization more effective. It's just highly challenging to do that from the bottom or middle. There are a couple of key obstructionists who have a lot of power and therefore can torpedo ideas that would change the company for the better. There's also very limited opportunity for advancement, and no program to groom or retain high performers.