Vantaggi
I'm a Consultant, so i'm slightly insulated from some Bank policies and politics, but i've been very impressed at how collegial, cooperative, and consistent the groups i've worked with are. There's LOTS of politics, but you'll work with the best and brightest from every point on the globe, all focussed on reducing poverty. Great cafeteria and benefits.
Svantaggi
Often the Bank seems like more of a place for people to pontificate and discuss, rather than solve. Getting projects approved, especially if they involve a change from the way things have been done in the past is challenging--just try to explain the benefits of using facebook on a communications project to a senior manager who's only interaction with the internet is through email.