My take on this:
What is life like at UChicago?
Amazing, in my opinion. You have to be willing to put in the time to study- there is a lot of work. But there is time for fun as well. The good thing is there is a lot of flexibility: if you are serious about studying, take honors math and a honors science, and you will get a great education. If you want to have a lot of fun, do econ, take the normal sequences, and you will have a lot of time to have an active social life, while still getting a pretty decent education.
What do students do for fun?
Party, dinner downtown, movies/tv, fun with their house, etc. There is also a ton of high quality free food almost all the time!
Do they mainly stay on campus or venture off?
People usually stay within the proximity of campus during the week, probably going down as far as 53rd street (urban area with lots of places to eat in Hyde Park). During the weekend, people often go down to the Loop.
What is the surrounding area like?
Pretty nice actually, I never feel unsafe. I don’t go south of 60th Street though 
Are the academics cutthroat, so much so that free time is rare?
Not at all cutthroat. I am taking some rigorous sequences, and everyone has been very helpful. I have 3-4 study groups that work together with me. So far, while the workload has been very heavy, the exams are not that bad- I like it because I can focus on learning a lot, and get good grades without having to waste time and energy competing with others.
What do you think is the best thing about UChicago and what do you think the worst is?
Best Thing: Profs, students, staff, campus, resources, free stuff, and the academic environment.
Worst: The weather.