Pros
In work one rarely gets the opportunity to build something new. This is a place where the sky is the limit. If you can dream it you can make it happen. People are friendly and open to new ideas. The CEO and other C level executives show that they care and want to hear from staff. And they respond to staff input and take the time to have town hall meetings and answer questions in real time. They don't just answer questions, they take time to explain why decisions were made and what factors were considered. They even know your name and remember it. This is most unusual in my experience! It truly feels like a family atmosphere. The benefits are industry leading in many areas and it really is a work hard and play hard environment in the best sense of the word. I have not seen the usual zero sum game politics here, it seems much more of a consensus driven rational approach to decision making which is great. All in all the best employer I have had in the last 20 years !!
Cons
If you cannot handle change and a fast pace then a growing dynamic company can be stressful. Having said that there is a good work life balance!