Pros
Excellent pay, benefits, and culture. The organization is very open to innovation and ideas that can help grow the impact and scale of the work. They take into account employee contributions, are very supportive in projects, and you can see the results of your work. They celebrate accomplishments and recognize employees. Very supportive HR (yes, a non-profit with an HR department!), provide opportunities for development, and work-life balance is greatly encouraged. They are not afraid of making tough decisions that protect employees and build a great company culture. They talk the talk and walk the walk.
Cons
Teams were relatively small for the workload and there were unclear paths to promotions. Both of these issues were being addressed near the time I was leaving, so I believe the situation may be better or fully resolved by now.