Pros
Fast paced but not in the traditional/negative sense - there is a lot you can accomplish, but you're not pushed to work at an uncomfortable speed or ridiculous hours. It has all the benefits of a modern small company without the overworking or stress.
The product is unique and there is a lot of growth promise. It's positioned right at the forefront of an exciting and prosperous industry.
You have direct access to everyone here, from the very top down, in fact your first week is focused on getting to know the whole team so you feel like an equal participant. Everyone is super friendly, and will take time to explain whatever you need. In addition, they make you feel respected, listened to, and a critical member of the team from the get-go.
Incredible benefits - it's clear that management LOVE this company and want employees to love it just as much.
Cons
People who are uncomfortable with lots of change might find it hard to adapt, especially if coming from a larger organization with clearly defined roles. You have to be good at writing up your own tasks, metrics, and growth objectives, although you are well-supported in achieving them.