Pros
Realistically speaking, the general difference between the top programs available are trivial, and ultimately comes down to specific research interests and the available faculty, though departmental requirements for chemistry are very lax, letting you choose any courses that would be useful for you, regardless of department, and no specific course requirements. Of course, Harvard gives you access to amazing resources in the area, particularly in biomedical-related fields. It's also in Cambridge, which is great if you enjoy the college-town/academic feel, but also gives you access to Boston. Undergraduates here are a pleasure to teach, at least in my experience.
Cons
Campus swarms with tourists every day of the year. Most surrounding restaurants/accommodations in the area cater to a price range a few steps up from a graduate student stipend. Rains a lot, Boston area is wet.