For books and movies and other topics where the reviewers thoughts are going to be more subjective I will rarely pay much attention to a review or even read one. In most of those cases I'll read an excerpt, the back cover, watch a trailer, or whatever will let me make my own subjective decision.
For other things, hardware, and the like, I use reviews heavily. I'll read a few of the positive reviews but focus mainly on the negative ones and looks for trends and/or consistency between them. And then, every so often, go get the thing anyway
