Pros
Generally good people who are good at their jobs. Most employees, from PMs to Analysts to Developers are good at what they do. Very relaxed working environment, lots of planned fun like parties, trips, lunches etc. Working here allows you to gain experience wit multi-billion dollars companies and foundations as clients. Unlike most agencies, they do not like to hire unless they can sustain the positive as a permanent one. I haven't seen post-project layoffs since I started and don't think there have ever been any. That being said, that strategy can also cause some added work to the people who do work here.
Cons
Work hours are up and down and typically higher than is acknowledged. Management is young and inexperienced, which in some cases is great but mentorship is lacking and career path can feel very undefined.