Pros
An incredibly meaningful mission and inspirational leader, President David Miliband.
Cons
Speaking only about headquarters personnel in NYC, they are not as transparent and progressive as they mean to be and many at the higher levels are free range, not following general leadership principles. Strategies are strong and impressive (with the IRC providing impact reports like no other humanitarian organization); culture is a drain with lots of outward cheerfulness that is more of a "show" than reality. That said, there are lots of incredibly talented people and if you are presented an opportunity, I'd suggest investigating whether the culture I've mentioned will be overcome by your love of the mission and the many wonderful people who work there.