Pros
Competitive pay, pension, and benefits. For interns, levels one and two, if you luck out and get a good supervisor, and are smart + work hard, you'll have lots of opportunities to get promoted quick, because people are quitting constantly.
Cons
A lot about your day-to-day can change quickly for the worse based on leadership (which is constantly changing) and based on random things the Board or loud rich people are mad about. The teams that need the most help are overworked and don't have enough people. The CEO and most leaders don't care about keeping employees. The agency would rather burn a ton of money on useless consultants than stop to think about how to develop and keep a robust team of full-time, knowledgable staff long term. Leaders don't trust their staff to make any decisions - lots of micromanagement slows everything down. Leaders frequently have you spend a ton of time working on something and then completely change direction of what they want, so all your work goes to waste.