Pros
Inspiring mandate and if you are lucky and have the right connections you might get a more longer term role with exciting work opportunities and can advance in your career.
Cons
As a consultant you're doing the job a P staff except your pay is a lot lower and you get no benefits or job security. Contract may or may not get renewed and they let you know very last minute. In my case I was told 3 days before the end of my contract that it wouldn't be renewed and that they had decided to replace me with another consultant. A lot of internal politics and throwing people under the bus, people spend a lot of time bickering with each other and talking behind people's backs. You get hired if you know the right people, not because of your skills or experience. Very bureaucratic and stiff organization, and very few females on leadership positions (most consultants and junior staff are women) and the leadership claims no responsibility to improve the gender balance.