Pros
A very fun workplace setting, suitable for young people. Open culture encourages everyone to know exactly what's going on internally. For engineers, you have a wide range of team choices, and you are given the opportunity to learn something completely new. There are a ton of great benefits and you will end up meeting and learning from very intelligent people. Opportunities for growth happen very quickly from what I have seen and people genuinely care about each other. The open environment encourages you to step out of your comfort zone.
Cons
Work life balance, or lack thereof. This will depend on your team. There are teams that work long hours and weekends just because they love what they do, or they want to meet a deadline, etc. It can be difficult to have work life balance with smaller teams, but it can be easier to control with a larger team. There are a handful of negative people at the company that look down on interns or new hires even though they themselves just started a few months ago. Some people get very sensitive about the products they own, even if they are just internal tools, and are surprisingly very unopened to criticism. In the end, it's about the money. If a product is doing very well, there will be a huge hiring push, which can be overwhelming at times.