Pros
Looks great on resume. Provides amazing exposure to high profile clients (depending on assignment). If you play your cards right and are willing to put yourself out there, you can have access to some of the great thinkers in the PR industry today.
Cons
Edelman is definately a powerhouse PR firm, but the things that make it so great don't always permeate down to the mid and lower level management, making it hard to really learn and grow within the internship. Your experience is solely dependent on which account you are placed on and under which management. Embarrassing and uncomfortable lack of diversity, both in background and demographics. Very little feedback. NY office is not for the weak-minded--you have to be aggressive or you will be left out to dry.