Pros
People are intelligent, thoughtful, communicative, and fun. Everyone cares deeply about the work they do, whether they are motivated by the mission or the technical challenges, or just getting to work together.
There is a lot of room for professional growth, by virtue of being a high-growth startup. The cool thing though, is that management makes room for you to pursue ideas and supports your growth.
Culture is very transparent. Everyone reports on their projects, asks questions, surfaces bugs, etc.
Cons
The teams can form into clicks to some degree, so you have to have a reason to interact.
Slack is life.