It is not as competitive as most people make it out to be. For the most part it will depend on what you major in but speaking as a chem major it isn't hard to score 35-40% above the mean on exams and thus set the curve - for example, in the 30 series (organic chemistry) - with a modest amount of studying. I guess there isn't much competition at the top
Of course there are professors who make their courses unnecessarily difficult, like Biskup, but they are somewhat rare. You will probably find more 'easy' or slacking professors than difficult ones here, I'd say. One thing though - it's not the material that makes a course hard, it's the professor who makes it hard (i.e. GPA killer). But these professors do have a reputation for their difficulty, and you most often will know this in advance when signing up for classes if you look for it...
As long as you are aware of this (i.e. try not to take classes with needlessly hard professors - e.g. Biskup - though this will sometimes be unavoidable) and know your strengths (study when you should), you'll do fine. Try to understand the material and immerse yourself in it as well as you can, and I guarantee you you will beat the curve, no matter the subject. In this respect a lot of the students here aren't really very good at this at all - they aim for a superficial understanding of the material and it catches up with them in the end.