Pros
-Interesting problems to solve. The product is quite unique, so are the challenges. -Decent benefits for a startup. They want to compete with big names on the market. -Lots of smart people there. Same thing - they want to compete on the market and attract "the best".
Cons
-Cliques and favoritism, as many already said. -Management that maybe knows some basics about managing, but has no idea what the term "leadership" means. -Small company with corporate-grade internal communication issues. -The stereotypical traits of a startup: "self organized flat structure", "scrum/agile", "extreme programming", "TDD", "not-invented-here" etc. Most of it feels decided in advance without any room for natural evolution. The outcome is immature/inefficient work culture, even 6 years after funding.