Well premed is a cruel prerequisite to one of the most rewarding and respected careers out there.
Beyond simply the difficulty of getting into med school, I've discovered that many people simply dislike premeds. Non-premeds don't like premeds because they make the class harder to get a good grade in. I had a very good friend tell me the other day that she hates premeds (which was a bit awkward because I'm premed). Research professors hate premeds because they prefer grad students. It's as if premeds can't possibly be as interested in research as grad students. Never mind the fact that many premeds go into MD/PhD programs, go into research-oriented careers b/w undergrad and med school, and are generally the most dedicated and science-oriented people I know.
I interviewed for an intro bio position yesterday. Despite the fact that I am a senior biology major with a 3.9 GPA and only one B in the 10+ bio courses I've taken (and I have prior tutoring experience), the interviewer basically assured me that I would lose in any kind of tiebreaker with other candidates because I am going into medicine as opposed to grad school.
(Note: I have done pretty well as a premed at Cornell so I'm probably overly optimistic about premed. I've studied hard and gotten good grades. What do I have to complain about? There are plenty of students who study hard for bad grades).