Pros
As others noted, the flexibility here is great and lets people set schedules that work for them. Dress code is casual and many of the employees are hard-working, friendly people. The organization supports positive goals and gives employees a lot of freedom. GA tries to be involved in many endeavors, so it's often interesting. Some people loved it here.
Cons
When I was there the company was going through a lot of change and employee/project turnover. Many projects were terminated partway through or were not adequately supported for success. There didn't seem to be an overall strategy to anything. In fact, management seemed proud of how agile the company tried to be, while glossing over many instances of overpromising and underdelivering. I wish there would have been a stronger commitment to following evidence, data, and good science. I think it's a good potential place to start a career, but I've certainly worked at places that were far more professionally fulfilling and better at getting good work done. While I was there several employees were targeted and were prevented from being successful in their roles, seemingly in ways unconnected to their actual job performance. The CEO is often off site, and her brusque management style can be harmful.