Pros
Good office space, occassional parties in office. They have good brands, and belong to the Publicis Group while Leo Burnett being their parent company. Certainly will gain you great exposure and experience working on good brands, and with such a big company.
Cons
Long working hours is the biggest problem. I have gone home at 3-4 am constantly, twice I have gone home at 9 am in the morning. Such pressure is unfair. Affects health in the long run. Also, senior management is bad. While at my time, I learned many employees there were formerly colleagues from another company, and so when it comes to politics, they'll all stand by each other and treat the junior management unworthily. All in all, the worst part is long working hours, and that was the reason I left.