Throughout my college experience I've only encountered a few really bad professors. Most of mine have been excellent and very flexable (one even let me take the final even though I missed it because I thought it was on a Thursday instead of Tuesday).
On the other hand, the ones that I would categorize as TERRIBLE are rightfully so!
I had this history professor my frosh year for World Civ 2. He was great at lecturing and made everything into a story of sorts. Well our tests would be all short answer and essay!!!! So when it came time you had five possible essay questions given to you so you could prepare and then a list of vocab words you should be able to write a paragraph on.
His essays weren't THAT hard to write about, but I soon realized after the first test that the JERK was going to be so frickin' picky that he had his own preconceived notions on what SHOULD and SHOULD NOT be included in the essay. You could basically have a notion of what happened at the Battle of Waterloo and he's still dock you if you didn't put something stupid in like what the army was wearing (something trivial)
.
Needless to say I got a D in his class, retook it that summer with a different professor and got a B+! GO FIGURE!