I was just looking at these forums today randomly for the nostalgia, and I had to make an account when I saw your post.
I was basically in the same situation as you -- I was accepted to a ton of very highly ranked schools, and I chose Duke Chemistry! I chose it because it was the nicest, most comfortable, most welcoming, with a large number of labs that interested me. It was also close enough to family and SO, and had the lowest cost of living by far!
Since the day I started at Duke Chem, I have not regretted it once. Everything is great here -- high quality classes, very talented students, and very helpful professors. I honestly feel like every professor and every classmate has always been on my side. Whenever I was going through trouble, it felt like I was surrounded by professors doing everything they can to help me.
One reason people think it's great to go to a highly ranked school is because it's easier to get a job after. Well, Duke is in the Research Triangle, which is full of companies and schools that all know Duke well. So if you might want to work in the Triangle, Duke is a great place to start. Also, Duke recently hired a ton of new faculty in popular areas like organic chem and chemical biology, and they're doing great so far, so maybe Duke will be going up in the rankings soon...
Someone told me only to use rankings as a tie-breaker, but never as a main decision-making factor. Go with your gut, whether it's Duke or somewhere else -- you don't want to wonder later if you would be happier at that other school you loved.