Pros
Big name clients. Beautiful office. Easy commute from most areas of central NJ, south NJ, and PA. Really great people (junior). You will work on cool projects and see your work implemented on a grand scale. The company will never go out of business because the owners are ridiculously rich.
Cons
Before I started here, another employee told me "This place is like The Devil Wears Prada." I laughed it off at the time, but it turns out the statement was pretty accurate. The owners are some of the richest people in the state, and as such have what could be considered strange (but more often are seen as insane) operational practices. If you do not dress, speak, or even bank a certain way, you are going to be put on the naughty list fast.
There is an extremely aggressive air in the office, leading to short tempers, over-competitiveness, and backstabbing. This is probably due to the amount of firings, quittings, affairs, and other drama that goes on. If you are not a favorite, your daily work will be hellish at best and nonexistent at worst.
During my time at IA, I witnessed administrative and HR practices that are hugely immoral, and possibly illegal. It is no secret that the agency and its management have been involved in extremely shady business... let Google do the talking. Oh yeah you can expect to be forced to attend themed parties or lose your job.