"There are very few negative adjectives more brutally crippling than “pretentious”. Very few can whittle away any pleasure from that description, and it’s often the kiss of death word when analyzing anyone’s artistic work.
Think about it. What sort of images does that word conjure up when you hear it? Since music is such a large part of this site, we’ll attack it from that angle. To me, I usually conclude it’s probably something totally devoid of anything fun, first and foremost. Long and meandering songs that don’t really go anywhere, full of lame sociopolitical/interpersonal messages that are of importance to no one except the creator. Something Robert Christgau would definitely drool over. Nothing you could really play in the presence of other people in the fear they would waste no time asking “What’s this shit?”"
Read an interesting article about pretentious and arty music: http://www.popmatters.com/pm/post/168678-pretention/