Pros
A complex organization presents many opportunties and different directions you can take your career. You need to be willing to take initiative to map out and cut your own path. Leaders are expected to have career path conversations with direct reports, and help identify and advocate for your "next likely positions". In turn, direct reports are expected to think about their trajectory and bring forth a point-of-view on their 3-5-etc-year plan. Lastly, the people here are seasoned, bright, and friendly, and top leaders are world leaders in their respective spaces.
Cons
A complex organization presents an overly consensus-driven and and fairly politically-charged culture. You need to be able to diplomatically state your opinion without having others feel as is you've stepped on their toes or squashed their idea. "Constructive criticism", "healthy debate", "direct feedback" are NOT phrases I would use to describe the Blue Box culture. Rather, "yes-based" relationships with little to no conflict confrontation are the norm. I think innovation suffers because of this.