Pros
Great people. Great work life balance. Technical freedom almost to a fault. I've been at the company for six years and never even came close to wanting to leave. Obviously nothing is perfect and we may have had problems here and there but I've had a very long career and this is the best place I've ever worked, by far. You owe it to yourself to check this company out. I love my work and I'm not someone who is looking for career advancement with a new title. I just want to learn more things, and get paid more. I don't care what my title is.
Cons
The only con, for some people, would be the loose organization. MediaMath isn't the Army. Roles are not strictly defined. You will have quite a lot of leeway to carve out your own domain, to set and achieve technical goals. Of course you have to support your team's production goals but there is a lot of leeway in how you do that, depending on your manager. Some are more laissez faire than others.