Pros
Overall it's really an amazing work environment. People are super smart, talented, friendly, and passionate about the product and company. Very collaborative with no big egos or office politics. Leadership is incredibly transparent and there's a culture of individual contribution from the top down. Merit is given where it's due. Great work/life balance and tons of fun events, competitions, happy hours, etc. happening both in the office and off-site. Essentially, everyone works hard together to continually improve a product they're passionate about and has a lot of fun along the way.
Cons
Standard growing pains of a company during a time of high growth. Ambitious--but also exciting--goals for the company in every area, maintaining the current culture that everyone loves, and running out of office space--though this is already being resolved. All pretty much negligible in my opinion.