OK, I'm a Cambridge undergrad and this is what I dislike about the university:
-Collegiate status is good for making friends within college, but makes it harder to make friends at other colleges unless you actually try. Most of my friends at other colleges are, I have to admit, from TSR; some others are from various clubs and societies. Depending on the subject, it would be easy to have very few if any friends at other colleges.
-Stress. Yes, I am an historian, and yes we're stressed less than other subjects, but on the whole the culture of eight-week terms leads to a frantic pace of life and utter exhaustion. Everyone tries to fit in several different things, and a workload that would make people at other universities blanche. I have a friend at Warwick who wrote two essays a term for History; I wrote one a week. I spend about 15 hours a week plus on the river coxing, because it's very enjoyable- but it takes away a slice of my life.
-The Cambridge Bubble- unless you try, it's really hard to get to know what's happening in the world outside. In my first year especially I felt very cut off, but now make an effort to read the papers and watch the news to know what's going on. I also make an efforty occasionally to escape the bubble and go to other places, or I would go mad.
-Social things- people make a judgement of me and the kind of person I am if I tell them that I'm at Cambridge. As the first few pages stated from various people, we encounter reverse snobbery and just derision, or just feel terribly awkward- how do you reply to the question, "so you're really clever, then?" without seeming arrogant? I don't dislike being at this universtiy- in fact I'm proud- I just dislike people's reactions to it.
-Work- my degree is, basically, teaching me to blag and bull****. I'm given a week to read up to 20 different books and journal articles, and then expected to come up with something original. I'm expected to argue against and disprove professors who have spent their lives working on the topic after maybe 10 or 15 hours of reading (it should be 20, but never is). Essentially, my degree is teaching me to be arrogant and assertive, and I don't like it.
-Loneliness- yes, even surrounded by 20,000 other people, you can feel lonely. My degree is very solitary- even the other historians never do the same topic, so it's very lonely, with no-one to compare yourself to or anything.
-Inability to form normal social relationships- everything you do is compressed into a shorter period of time, and this includes relationships- I don't see my girlfriend as often as we both would like, and rarely if ever during the day, because of work and boring stuff like that.
-The essay grind- not necesserily so applicable for science students, but doing an essay a week every week really takes it out of you. You can rarely if ever be completly satisfied with your work, and there came a point last term when the last thing I wanted to do was to sit down and write another week's essay- but had to.
-Exams- yes, they're just as bad elsewhere I'm sure, but here the degrees are very traditional and not modular, so Finals count for a lot. Plus everyone is, basically, a geek or worse so there's a massive culture of panic and stress about exams. I'm quite stressed myself, though I've not shown it, to the point of being ill from stress.
-Elitism and "rah"-ism - unfortunately, it does exist. Yes it's never as blatent or offensive as I believed before I came up, but it does exist. People who've been to public school generally have an ineffable air of confidence and superiority about them, and are generally lucid and argumentative. Then there's just the odd people who get a termly cheque from Daddy, or a weekly allowance. It's going into Ede and Ravenscroft and being told that a suit, for me, is £600, and knowing that there's people who could easily afford it. Or people who have facebook albums of their holidays in Greece or wherever. Then there's just the occasional braying twit. Chip on my shoulder? Me? Never!