Pros
The people and the mission. You'll find a lot of like minded people who are interested in saving the environment. The benefits are good too.
Cons
Pay. You can make significantly more at other non-profits and it's rare to receive a pay raise or promotion. Senior leadership and upper management are the biggest grifters. Every few years they leave for better jobs and are replaced with similar people who sell a vision and restructure, but leave before the results come in. The next people do the same thing and this cycle continues to leave the organization worse off than it was before. The organization is very inefficient, spends money frivolously, and treats its employees like a revolving door. You join a non-profit to get away from the capitalistic private sector, but you are treated as a replaceable employee at a big corporation. Very few projects are completed on time or on budget. There are too many middle managers who just complicate processes and slow things down. The organization is bleeding money because of inefficiencies, poor spending habits, and high salaries for leadership, without much to show for it. As a result, there have been multiple layoffs in the last couple of years, with no confidence that the sinking ship will be righted anytime soon. Employees have started to unionize, but leadership has been dragging its feet during negotiations.