Pros
The opportunity to meet and work with some incredibly intelligent and talented people. A warm and collaborative working environment, where people aren't afraid to be honest with each other. Job dependent, the opportunity to travel to some amazing places. There is no perceived hierarchy; the senior managers are approachable and work closely with their teams.
Cons
It sometimes feels like budgetary restraints are never ending, from managers being unable to hire the candidates they want, to investment in software that would make work easier for a large group, being able to take a team on a nice lunch etc. Some people, managers in particular, might find the constant 'no' response to requests involving financial input frustrating / demotivating.