Pros
Great reputation with governments, partners and public in general. Doors open when you speak of UNICEF. Good employment package compatible with UN standards overall, especially for those with children. Organization attracts great talent, especially young people who are the ones who tend to stay longer if given the chance. Inspiring mission, charisma and overall objectives.
Cons
No work-life balance: in fact, not having a personal life is rewarded, celebrated. Promotions seem to be more politically-related - your connections matter more than your capacity; no merit in working hard if you're not ready to play some heavy politics. Leadership often rules by fear and intimidation. Huge, inefficient bureaucracy. 30-year-old policies and systems in place; implementation is poor and admin staff do little to support program staff and managers to ease processes and unlock bottlenecks. Frequent tensions between national and international staff members. When senior talent is recruited from outside, little effort is made to ease transition into the organization, leading many to leave after a short period with the organization.