Pros
I was with the company for 4 years, and I was fortunate to always have other options. However, I stayed because of + World-class founding team with a strong track record of success, who are all personable, fun, and approachable + Smart, capable, and friendly co-workers + Strong vision for the product in a compelling market + Clients include some of the world's largest and most successful companies + Fast and agile pace, with new challenges coming at a rapid clip + Thoughtful company -- people care when any issues arise (professional or personal) + Of course, the perks that you expect at a startup, from lunches to fun offsite events
Cons
It's a startup, with employees distributed across the globe. So, of course there have been growing pains across departments. But over the 4 years that I was there, the core leadership actively solicited feedback and always worked to improve the company.