Great working for a company with a mission. Currently undergoing changes.
Pros: Good people, great benefits, mission-driven.
Cons: Bureaucracy, focus on consensus building can slow things down to a glacial pace.
At KP, I've worked with some of the kindest, smartest, funniest people I know. During our department's "golden age," growth was available for anyone. I asked for more responsibility, more variety, stretch assignments, and I got them. Really grew in my capabilities and worked on some pretty cool projects.
They recently underwent a re-org, and things have changed significantly, which is unfortunate. They are still good people, but the approach and management is markedly different. Tighter supervision than before. Less freedom, even for high performers.
Great benefits. Decent pay (probably competitive for a nonprofit). Advancing can be tricky. But the place is massive, so a lot depends on what department you are in.