I'm going to take a moment to direct you to Rate Your Students, the blog that lets teachers vent about the behavior of lazy, disrespectful, uninterested students. While it lacks the radio-button numeric ranking system that so many institutions believe accuarately measures the quality of their faculty, it is generally more articulate than some of the complaints I've received on evaluations in the past.
While several of the posts do strike a chord, and I recognize the behavior of several of my own students in the descriptions (in particular, the ones who suddenly become very concerned about their grades just before/after the final exam, and assume that this last-second effort should automatically entitle them to a better grade), one thing this drives home to me is that I'm actually quite fortunate as an instructor. I teach a subject in which the students are fairly easily and objectively evaluated (I don't enjoy grading 300 calculus problems, but it beats 20 book reports any day). I've never taught more than 40 students in a term (and only that many when I have two sections), so I can learn all of my students' names before the first test - I consider this very important; a student who knows he/she is not anonymous is more likely to come to class, and less likely to be rude to the instructor. I teach an intermediate course; one where the students are often (but not always) more mature, both in terms of knowing the subject beforehand and understanding their role as students. And I don't teach at a public high school, where I would be little more than a babysitter.
I still plan on teaching when I'm done with this school thing. But stories like these will make me a little more open to those cushy private sector jobs.