Pros
Ending poverty by 2030 and boosting shared prosperity. These are the two goals the WBG wants to achieve. This is inspiring and makes the job really interesting. Your daily job can make a difference for many people in the world. The WBG offers very competitive salaries. Your colleagues are coming from all over the world and it can be a daily challenge to jongle between all the different cultures if you're not open to cultural diversity. Lots of benefits (holidays, sick and family leaves...) and a very good medical coverage (very good compared to the US, average compared to the European standards).
Cons
This is a bureaucratic and political environment. But once you learned to navigate these aspects you can get your job achieved. Very tough place for short term consultants. ETCs (1 year renewable once) are better treated and have many benefits comparable to staff. Takes time to change grade. Salary raised are opaque.