Pros
Unlimited potential for personal and professional growth due to current state of company's evolution. Amazing access to senior leaders with almost all employees on-site in Palo Alto. Leadership listens. Chance to have a front row seat at a late-stage private company. Opportunity to make decisions and execute on initiatives that will impact the company for many years to come. Passionate, engaged, and positive co-workers. First time doing almost everything: hiring at scale, designing processes and programs, re-organizing to meet medium-term customer and market demands.
Cons
No handbook for your role: either it's brand new or the role/org is changing too quickly. Pace of growth and change can wear you down. New middle management layer is still figuring out how to communicate and manage. Some people/resources spread too thin. Already quite quarterly metric/goals driven for a company that's not yet public.