I worked with some of the brightest and best people in the business. Most of them are no longer with the company.
Some good clients, and nice office space.
Cons
Very limited opportunities for growth. During my time they reduced promotions to only once a year, and made many excuses for promoting as few people as possible (despite becoming the first "$1B" agency at that time). Morale was extremely low. People were forced to come into an office with nobody they actually worked with. Common to be passed from manager to manager. At one point I had 6+ managers within a 10-month span.