I was an undergrad in the late 80s/early 90s, so things may have changed. But the hardest part of being there was the numbing boredom of having someone read/paraphrase the textbook to me and call it a lecture. Sitting there in a room with 300 other people, listening to a monotone paraphrase the textbook for an hour and twenty minutes, twice a week. It didn't take too long to figure out which of those lectures I could ditch. Only needed to go home and read the book in a day, then go back and take the tests on test days. As they were all multiple-choice scantrons (due to the size of the classes), it was a pretty easy 3.5 GPA.
The second worst thing was having to sit in a smaller class where many of the other students were functionally illiterate. Not only could we not do any accelerated work, we spent a lot of time explaining ordinary vocabulary words to the folks who hadn't had proper preparation for the class. It wasted a lot of our time.
Third worst thing was having a TA teach sections - someone who was not a subject matter expert, but who had to get up there because that was how he obtained his financial aid and "in state" tuition status for his/her master's program.
Fourth worst thing would have been, I think, sitting in the class with the stoners/drunks. There appeared to have been plenty of them. Then again, I remember having a beer now and then before having to go sit through some of those lectures. Made it bearable. 