Pros
There will never be another time in most J-PAL employees' lives when they can live in the field, with nothing else in their lives except helping to impliment programs that could potentially make a difference in needy people's lives.
Cons
There is a reason why people do not do this for their entire life. The organization requires constant work, gives little feedback and largely leaves RA's alone to fend for themselves, except when in emergencies it sends more senior staff to babysit them. There is no work life balance and very little contact with research. It is a lot of busy work, and I feel that many new comers are not accustomed to this kind of work. The salaries, benefits and balance aren't good enough to encourage more mature applicants.