Honestly, I've never even heard of the site, but I doubt I would take anything on there seriously. People love to say that professors suck just so they have an excuse as to why they failed the course, when in actuality, they were just lazy.
It is valuable to go there though and at least get a heads up. I picked a teacher with very little info (1 or 2 reviews maybe) and things started out well. Several weeks into the semester, her true personality emerged and her grading policies were BIZARRE.
As a competitive student trying to get good grades for med school, I don't consider myself lazy by any means. In other words I bust my ass in all my classes. I missed a quiz due to illness, so instead of letting me earn my grade by retaking it (would have lasted literally 5 minutes), she told me she would give me a score equal to the class average.
HOLD UP - average scores usually comes out to about a C, and this was going to be no exception because the people in this class weren't the brightest bulbs. I was gonna get points (or lose points, if you want to look at it that way) for what
THE CLASS DID. Not myself. Not what I earned.
Strike 1.
Then she assigned us group projects; one online discussion board assignment had specific guidelines to follow which probably 3 out of 6 group members actually did. The other 3 didn't do anything to participate at all - they chose to sit on the couch or party that weekend. The 3 of us that participated tried to make up for the fact that the rest of the group did nothing by having more discussion responses and replies. Instead of earning points as individuals, we all got 50% on the assignment. The hard workers got an F. The lazy workers got an F.
Strike 2.
I consulted her shortly afterwards about what we had to do as a group to get an A for any future assignments like that. She said that we had to consult the group and make rules for them to follow. I asked her,
"how are we going to force them to do anything if grades are not a motivator?" where she replied something like
"thats the trick.." I was in utter disbelief. The only way I was going to get these group members to participate was either 1) paying them off or 2) going to their houses and becoming violent. Wasn't really down for either.
Strike 3.
Anyway, almost a few weeks after that, a whole new batch of bad reviews popped up for this teacher. I agree that the people who feel shafted are the ones who put up bad reviews, but just because they put up bad reviews does not mean they were necessarily lazy.
I think it never hurts to know what other people have to say. It never hurts to be educated on your teacher. All I know is I'm never taking that prof again.