If you want to make the world a better place... and you have quite some patience
Pros
The themes dealt with are extremely interesting, what you read on the newspaper every day, and with a meaningful purpose. The colleagues are from all cultures: this requires some skills and sensitivity to manage but at the end is extremely enriching. There are a lot of opportunities to do interesting things and learn on the job. If you have sense of initiative and unless your section is under strict political scrutiny or your boss is not supportive, you will have the chance to introduce and implement new ideas. The salary and benefits are very generous. The working conditions are above average, if not good in most of the cases (of course more difficult on missions).
Cons
The most frustrating thing is the gap between the big ideals and what is actually done to deal with the world problems, but this is not only the fault of the organization itself. The bureaucratic burden is often unjustified and makes doing your job more complicated. There is no real HR management in the organization and despite all strategies and programmes, staff are pretty much on their own for what concerns their career. Even if it should attract only highly qualified staff, the truth is that it is like in any other working place, with some very bad individual who can be a real nuisance, especially because once they are in the system, there is no way to manage or separate them. Many managers do not have any managerial skill at all.