Pros
Gives interns a decent amount of responsibility, take the work they do very seriously, work with variety of clients, overall good place to get introduction into world of marketing, communications, etc. (in its both interesting and dreadful aspects) fancy free lunches with your team and the partners
Cons
Pretty scattered in terms of assignments. A lot of "here, do this!"--could make it hard to feel like you were really working towards something or knew what to expect on a day-to-day basis. A lot also depends on what team/client you are working with. I personally felt really disconnected from my team and never ended up getting an official onboarding process. Made it feel like my work was unrecognized and didn't matter much. This was enhanced by everyone seeming so busy that they didn't have time to even answer a simple question. Also, they could have paid way more for a fancy advertising place in NYC that regularly goes out to expensive lunches.