Pros
The United Nations promotes the highest of ideals with a purposeful and essential mission. You will have a nice salary and excellent benefits as a professional staff member, but unfortunately young staffers and contractors have little job security. You may also be lucky enough to have incredible colleagues from all over the world, and a select few are doing the best they can to help implement positive reforms in a mostly broken multilateral system.
Cons
Mostly incompetent middle managers and even some senior staff, little to no job security for consultants and contractors which are heavily overused, excessive wasteful spending, paralyzing bureaucracy, little accountability and transparency, slow recruitment process with little to no feedback if you’re lucky enough to get any at all, political dysfunction largely due to member states, hundreds of harassment cases every year with little to no punishment for abusers, culture of impunity, inability to show results, slow procurement process, risk averse culture...shall I go on?