Pros
By far, the biggest pro at Mediaocean is the peoople. Every single person at the company is amazing, and I've never encountered a situation where someone did not want to go above and beyond to help you. I made so many close friends at Mediaocean, and that speaks volumes about to the types of people they hire. Another pro of Mediaocean is the culture. There is a "work hard, play hard" mentality, and while everyone is working hard, everyone knows how to have fun. There are several social events held in the office during company time, and everyone from individual contributors to the C-suite kick back and relax. The work-life balance is second to none at Mediaocean. There is an expectation that you perform at a high caliber, but management (at least those in my reporting line) were very liberal with your work schedule. As long as you get your work done on time, you can work from home and take time off as needed (as long as you get supervisory approval and don't abuse it).
Cons
One con to Mediaocean is that compensation can be below industry standard. I can only speak for my personal experience, but a candidate with my years of experience, skills, and education could easily be making $5k-$10k+ more elsewhere. You have to keep in mind, though, that some of the benefits (like the flexible work schedule) can make this a non-issue for some. Another con is slow career growth for some. As I wrote above, every single person at Mediaocean works hard, but I saw some people make several jumps in title in a short amount of time, and others that I thought deserved a promotion be passed on. Added to this problem is that there is not a clear career map for most positions, which makes the promotion and compensation process extremely vague.