As a student, I do use RMP to help me determine which professor to take

But .. I don't blindly believe everything. I know most of the negative reviews are from idiots/lazy people who are just angry the class wasn't an easy A. I weigh in the good reviews more heavily than the negative ones.

Or if let's say I'm torn between 2 professors who both have mixed ratings, I'll go with the one whose exams I would prefer (i.e. one's exams are multiple choice, one's are short answer, so I'd go with the multiple choice). So RMP helps me in that regard too

But when you have a professor who has 90% bad ratings and even the good ratings are all Bs, no As etc, yeah I won't take that professor. I.e. I have a friend who is very intelligent and gets As in everything. She then took a professor like the one I described and .. surprise .. got an A- even though she worked her ass off. I'd just rather not take any risks (I need as high GPA as possible for my graduate program), and so why take that professor when I can take someone who will make my life less difficult, but teach me the same material?

I think if anyone takes those reviews to heart though you wouldn't want them in your class anyway.