'On the other hand, MIT did somewhat cultivate an exclusive attitude among its students-- particularly the undergrads. During my time there, I felt there was a pervasive strain of "We're the best in the world..." getting shaded into "...therefore nobody else is any good."'

Really? I never ever felt that way during undergrad. I interacted with many grad students and every single one seemed more capable than I would ever be at their field (not self deprecating, just a true statement). While I would like to speak on behalf of all MIT students to say that this isn't likely, I can fully see this happening in small social circles. Maybe I got lucky, but I just never really saw this happen or felt that way towards grad students.

While interacting with some Harvard students, I definitely felt like I was the "lower pedigree" though. This is probably due more to the Cambridge rivalry than anything else though.

MIT is a pretty stressful place for grads and undergrads a like. Sometimes social skills aren't necessarily placed at the top of the list when there are many PSets, Exams, and other items above some pecking order ;).