Vantaggi
The people are great. They are good at what they do, they care about what they do, and they are easy to work with. They will push for change when they see something can be improved. People who "don't play well with others" are aggressively filtered out as early as possible (usually in interviews) and are remarkably absent from the company. The company is very well run. It's a company that is light on process, and continually reviews its process to make sure it's doing what it's supposed to do, and seeing if it can be improved -- bad or useless process is discarded and replaced. The company works on something that matters. It's not solely focused on making money to the exclusion of everything else, but rather in building something useful for the world. The vacation policy is generous, and management works to make sure that people take advantage of it. The company is growing fast, so there's a lot of opportunity for growth, either moving up in management (if that's your thing) or moving across units for personal technical development.
Svantaggi
While the company is growing, it's still relatively small. There is a lot of opportunities within the areas the company is focused, but there are still many areas someone could be interested in that aren't covered by the company today or in the near future.