Pros
Great group of people. Management takes hiring very seriously so they have a team of talented employees who all enjoy working together. Good organization with clear direction and goals lets everyone own their own schedule and drive their own productivity. Transparency is a major theme, pretty rare in most companies. There's also a level of fulfillment associated with working on a problem that really matters and can make a meaningful difference for a lot of people. If someone walked into the office any given day, there's a 50/50 chance that the employees would be in quiet focused meetings, crunching numbers on their MacBooks feverishly, OR having a soccer tournament in the middle of the room in their socks while arguing the merits of Chipotle's new queso. I genuinely look forward to going to work every day.
Cons
Small team working on a big problem so you're never really done. If managing your own work/life balance is a struggle, it's easy to tip in the work direction here. This environment really only works if you're very good at self-management. Lots of distractions available, and not a lot of hand holding.