Pros
As many of the other reviews mention, lots of smart and capable people. Interesting problem space and intellectual approaches to solutions. Fun happy hours.
Cons
The engineering culture seemed reminiscent of the much debated culture of amazon, in which everyone down to the individual contributor level must take responsibility of development work, QA, hiring, product management, client support, requirement gathering, and prioritization of multiple projects. It felt like the engineers were stretched far too thin which in turn created not only bad products but large waves of attrition. Also, they seem to have difficulty with appropriate resource allocation, in that they assign people to projects that don't cater to their strengths or approve teams who insist on spending their work hours building and supporting crazy things outside the scope of adTech (think Atlassian products...). The lack of organization between product, client support, and engineering made it very hard to get anything done here. I hope they have since or will change their methods.