Charles Wang, I received my Bachelor's from UChicago in 2011
The workload is heavy, but this is true at other schools as well. What both the faculty and students reinforce is a strong sense of Intellectual rigor. Academic intensity is strongly reinforced by the culture of the place. You will be expected to tackle difficult questions, and be challenged and taken to task for sloppiness and lapses in thinking and logic both in and out of class. The curriculum itself often has dense and esoteric elements too, as anyone who has taken the Core and read Hegel or Foucault can tell you.
Combine this with bleakness of the winters and the social awkwardness of the student body and it is easy to for some students to feel alienated and exhausted.
That said, the school isn't really competitive in the conventional sense (and so lacks some of the pressure-cooker dynamics of other schools). When I attended UChicago I never really had a sense that people were preparing vigorously for their professional lives, but rather that they were there to inquire and learn.