Pros
Since it's still a startup there is a lot of opportunity to take on new challenges, whether it be new features to be verified or inventing a better process and sharing that with the rest of the company. Not only is the work more interesting, but personally I've learned a LOT more in my few years here than at my previous company. I'm so glad I took the leap to join, and I would strongly encourage others to do so too.
Cons
My only complaint is that we haven't gone public yet