Passionate people and a great mission, with normal non-profit pitfalls
Pros
Everyone I worked with was passionate about the organization and committed to success. In my role from a centralized office, I was also able to observe and experience the amazing contributions being made across the Institution, and having insider access was one of the best perks of my job. Being based in the fundraising arm of the Institution, it was rewarding to see the passion that Smithsonian donors also brought to the organization. As with most large organizations, team dynamic is crucial, and my immediate team, along with my broader team, was predominantly welcoming and collaborative. Some areas of management need improvement, but overall it seemed to be moving in a good direction. Great work/life balance, good health and retirement benefits, and reasonable pay for a DC-based non-profit. Nice staff discounts at the museums, and being able to enter museums through the staff entrance (read: bypassing the lines) was an incredible perk, particularly during busy tourist seasons.
Cons
As with any large organization, there are wearisome internal politics, particularly once you add in the 60/40 federal/private dynamic (and be aware that government shutdowns affect the organization). Just as the benefits mimic the pros of government systems, so too does the pay scale - it is extremely difficult to advance within your role. To advance, most people must leave the organization or move between different internal units. With high turnover, people who want to stay often take on much more work than originally hired for, without the benefit of promotion or increased salary. Also, despite my department's efforts for strategic planning, priorities often shifted rapidly and without much notice. Multiple projects would get started and then shelved.