Pros
I've only been with the company for a short time, but it's already one of the best places I've ever worked. The company is filled with truly talented people who want to build a great culture. I've never seen so much employee initiative in organizing clubs, social activities, and volunteering events. Quantcast reinforces this by investing a lot into employee happiness (happy hours, catered meals, corporate outings, team building, onboarding events, etc.) and upper management seems to genuinely care that everyone feels like they are a part of the team and helping to build something great. As an example, the CEO still takes time to personally talk to all new hires, which is crazy for a 800+ employee, global company. I met him quickly at a remote office and when I was visiting the corporate headquarters, he remembered me and stopped what he was doing to have a conversation with me in the hall. That would have been unheard of at any of my previous employers.
Cons
The company is growing very quickly and with that comes growing pains. In trying to create scalable best practices, new technologies and processes are attempted and sometimes quickly abandoned or changed, which can create confusion.