Pros
The culture at Two Sigma is unlike any other financial services firm out there. Two Sigma goes above and beyond to ensure a pleasant work environment and proper work-life balance for all its employees. From the laid back dress code to the encouragement of working remotely to the fully stocked kitchens with loads of healthy (and some unhealthy) snack options to the standing desks provided to any employee upon request to the monthly catered company lunches... Two Sigma clearly cares about its people.
Cons
It's going through some natural growing pains right now, where it's becoming increasingly difficult to maintain that "startup" vibe. Bureaucracy becomes somewhat inevitable as growth happens, but it's still remarkably less than at any of its competitors. Also, while the flat structure can be a nice equalizer, it also makes it a bit trickier to grow within the firm, although certainly not impossible.