Pros
Great team, very friendly and helpful coworkers, great location, free lunch twice a week, modern office with lots of light. There are some project managers coming on board, which may mitigate some of the cons.
Cons
The cofounders have never run a company before, and it shows. One of them has published research on unconscious bias, including in hiring, and his experience should have helped the company build more diversity by now; but he won't step in and get his partner to stop policing the diverse hires harder than the white guys--his partner's bad behavior has already chased off two full-time female developers (out of a total of four), plus who knows how many interns. Aside from his anti-diversity issues, the techier of the founders also can't let go of control enough to let his employees do the work they're hired for. He micromanages everything from onboarding junior developers to architecture decisions (this, he does well) to fine-grained development decisions about the software. If he would step back and stop constantly changing project priorities, people would get the same amount done, better, with higher morale and more time away from the office. As another commenter mentioned, almost the entire development team is young, first job out of college, and the interns outnumber the full-time employees, especially in the summer. So there's an undercurrent of hard-drinking, hard-partying that not everyone would appreciate. The salaries here are significantly lower than market rate (it's a non-profit), and the hours are long; my theory is that most of the development team doesn't know they have the option to be treated better and paid better elsewhere, and that's why they stay.