Pros
The work is interesting and constantly changing (never get bored!). There are always opportunities to learn and try new things. The people are amazing with lots of varied experience. Also though, they are genuinely kind, intelligent, scrappy, & driven individuals. It's an honor to have the opportunity to be exposed to so much talent.
Cons
There's definitely a lot of ambiguity here compared to a longer established company. The upside is that the maturity of the people helps cover for missing structure. However, in the long run, scaling up means also creating structure and process (which is going to be a series of trial and error). The only other con I can see is around managerial experience compared to a large company. Managers are often used to holding many hats and juggling them, so experience in delegating, communicating, and creating process can be a little foreign. That being said, they are also already working on continuing to educate their managers with regular managerial coaching sessions.