Vantaggi
The work is interesting, and you work in a diverse environment, with smart people. There can be good travel. Work life balance is very good, few work more than 40 hrs a week. Perks are good (vacation 5 weeks, pension, health care), but there is no bonus at all.
Svantaggi
Its a very flat structure, so there are few opps after grade G especially. Its incredibly bureacratic and slow. US and EU nationals (especially men) will find it hard to get on - there is a huge push for gender and national diversity. If you are a woman from Sierra Leone, with a US/EU education, you can do very well indeed. The mission is noble indeed, but the onyl thing anybody really cares about is lending as much as possible, as quickly as possible - so its more like a traditional bank than you may think. Informally, most people will tell you they don't think the WB makes any impact on poverty reduction, but they work there because its easy and its in DC/USA - which is usually a nicer location than where most employees come from. Easy visa route into USA (via G4 visa).