I have been sending students to SNU for last 5 years. Most of my students join there for BMS or Eco. Some have joined for maths too.
Going by their reviews, the place has lot of positives and few negatives. But, as the question is only about negatives, I will list some here.
Distance: the campus is far from everything, it seems. So, if a UG student wants to prepare for exams such as CAT, GMAT, GRE, UPSC then it becomes difficult to get a coaching nearby. Travelling for 2 to 3 days a week becomes hectic.
One more disadvantage of distance is that some professors are not residing at the campus. They travel to the campus from nearby cities. They also complain about the hectic nature of travelling.
Too many electives: SNU offers a high level of flexibility when it comes to course curriculum. They offer wide variety of courses across departments. A student of management can do a course in some other department if he is interested. Even IITs and few other colleges have that facility but they also don’t offer these many options.