In the last year or so I've noticed lots and lots of British independent films on there, with actors I liked, and decent sounding plots, but really low ratings, but started to check them out regardless, and discovered that most of them were actually quite good, and very undeserving, in my opinion, of their low scores.
These films are likely to only be rated by a few thousand people, so it won't be as accurate, IMDB has this problem with a lot of films. I have also seen it go the other way and films I thought were bad were over rated due to the small amount of votes.
With IMDB I treat it as advisory, If I really want to see something I will see it whether the rating is good or not. When it is good is when you can't decide what film to watch and you can pick the one with the highest rating.
I don't however read user reviews anymore on the site. Too many times have I been about to watch a film, read some user reviews then see one written by some idiot who just summarises the whole film, and drops a big spoiler in somewhere without marking it as such. It's also annoying when you scroll too far, see one of the posts from the message board, and the title of it is a big spoiler.