I agree with Bags and Bearman, in that using pitchfork as a complete guide to what to like is pretty absurd. And, I'm sure people do that even though they'd probably deny it through and through and most likely don't even realize it themselves.
But, it can be very difficult to learn about music, and in pitchfork's defense, the website has a great layout, is extremely accessible, and is updated everyday. Plus, its a great thing for indie rock music as a whole. It gives those indie bands who develop a new sound a chance to be heard. To say that the writers are pretentious just because they give some bands bad marks is stupid. That's how opinions work (at least meaningful ones), and yeah, take it with a mine of salt. My only qualm with pitchfork is the times when they try to be too creative and get sidetracked into other things than the music.
On a side note, I think that Travis Morrison saying that his fans no longer know whether to like him or not because of pitchfork is perhaps saying more about Travis Morrison/Dismemberment Plan than it is about pitchfork. If the Dismemberment fans were really diehard Travis Morrison fans, they wouldn't care what pitchfork had to say. Not to start any battles, but maybe Dismemberment Plan never should have been as popular as it was. Pitchfork giveth and Pitchfork taketh away.