Libby doesn't post here all that often, so I thought I (a current student) might chip in.
Chicago, along with being a prestigious school (as you saw for yourself in the US News rank) has a real focus on academics, and it is a passion for learning that I think draws many students to the school. Though the school is strong across the board academically, one of our most popular majors is biology, and because we have a hospital next door plus lots of on-campus research, there are a lot of opportunities to get involved.
Beyond academics, you have the typical college fare-- lots of student activities (really strong theater and Model UN in particular), and of course the city of Chicago.
Some more information-- if you have more specific questions, you can probably e-mail them to somebody from the website or ask them here again:
http://collegeadmissions.uchicago.edu/