Pros
Working for a mission-driven company makes for an engaged and enthusiastic workforce. Focus on impact means that you have flexibility to get work done when and how you choose. Quality of people we hire is outstanding, coupled with low egos. Love the 'focus on strengths' mentality which means your role often shifts to make sure you are spending the most time doing what you love. Lots of support and training for managers at FB, although the individual contributor role is equally valued - becoming a manager is a lateral move (and a deliberate choice) at FB rather than a reward for being awesome in an IC role.
Cons
Personally I love the concept of bringing my authentic self to work and being personal friends with coworkers, but I understand that it's not for everyone. I do feel that this will become more prevalent as the millennial generation becomes the majority of the workforce in the next decade.