Pros
Professional, organized, great at getting and keeping business. You can learn a lot from the people here. Lots of focus on career development, they really take this very seriously here, and make it clear that you have options to move laterally within the company if you are not thriving in your current position. They seem to be weathering the economic crisis very well and have a wide range of customers. They take a very long range approach to clients, trying to always be the agency on record (unlike many smaller shops, that tend to do one off projects and suffer enormously when economy tanks)
Cons
Junior people seem to go through the mill rather quickly and get burned out and bail in first year. The company can ask a lot, and if you're not used to setting limits you can get used up. It seems like sometimes senior management looks the other way while the kids are putting in massive hours per week. Happiness can be quite variable, depending on which group/project you are on. Some teams are ultra pro, some are pure monkey chaos and to be avoided at all costs. (But even monkey chaos here is better than I've seen at many other shops!) Senior people tend to have an easier time here.