Pros
It's an amazing place to meet people. I met CEOs, heard world leaders speak, dined with Nobel laureates. It also has unparalleled benefits, including great health care, wonderful facilities, and generous vacation policies. It's impossible not to feel like you're in the middle of something very important, because the people around you are literally in the New York Times day in and out. It feels at times like the center of the universe, and the brand name gives you good access to most of what you may want to do. Some of the professors are true visionaries and some of the students inspirations.
Cons
Contrary to popular belief, Harvard is not necessarily a great place to be an intellectual. The university places a higher premium on being important and untactful than on service to the Truth. This is probably wise (they are Harvard for a reason), but coming from a more naive and honest environment led to a little culture shock upon first arrival. There is a clear pecking order. President, University Professors, Deans, Head of Research Centers, Professors, Junior Faculty, Annointed Golden Children of Famous Professors... Staff. Don't fool yourself. Everyone has daggers under their cloaks and wants anything they can take from you. It's Harvard!