Pros
The team has a very strong ethos of hiring great people and giving them space to do great work. As an early stage startup, the priorities are in the right place -- focusing on great product development, scalable solutions, and best of all: giving us the room and the time to solve very hard problems. I and my peers have had regular opportunities to expand our skillset and be challenged in ways that were lacking earlier in our career. I've also had career advancement opportunities which eventually led to a promotion and raise. Benefits package is competitive, and there are nice perks like free Citibike, 4 volunteer days, etc... we work hard but there's a big focus on having a good work-life balance.
Cons
It's an early-stage startup, so it can be a little rough around the edges at times. While it doesn't bother me too much, I've seen a few people have ruffled feathers around lack of process in some areas. But over the last two years I've seen a constant improvement in this area. In the early days the team was small and we were finding our footing as a company, so camaraderie in the office wasn't as smooth, but as we've grown we've been finding our footing.