Pros
If lucky, your manager will take note of your ability and assign you to projects that help developing countries. If you have impactful projects in your portfolio, you gain useful skills and you really make a difference in people's lives.
Cons
The STC pay scale is ridiculously low (think $40K-$60K/yr for most people), even though STCs make up most of the people who work at the World Bank (Out of 20,000 people, around 12,000 are STCs). By comparison, permanent staff members (a minority of the 20,000 workforce) make about $175K/yr with full benefits and perks. You work beside them, and are expected to shoulder the same responsibilities and have the same deliverables. You are limited to 150 workdays PER YEAR. That is INSANE, and the poverty wages you make will never allow you to live well in DC. The organization culture is toxic, treats consultants as disposable, and offers ZERO benefits (no insurance, 401K, or ANYTHING ELSE). IMAGINE a professional role that requires a master's degree but offers zero benefits and no insurance coverage. You are told from day ONE that there are thousands of people waiting to take your place, and that you should be grateful to work there. Because of the 150-day-per-year limit, you are expected to underbill your workdays and work for free in order to last through the year. The organization's lofty goals of improving lives around the work and providing social protection become laughable when you look at how brutally it overworks its own people. The hypocrisy and gap between the Bank's professed values and its true values is painfully large.