The thing about the Mars Volta is that they are not the kind of band where you can listen to one song and make a decision on them. They aren't an "emo" band, they are an art-fag band, and a lot of people don't get it, and thus don't like them. To really appreciate them, you have to listen to their whole albums from start to finish, which means you need like a whole hour to just chill out and focus on the music. Their albums are stories. They aren't "singles" albums, and they aren't full of songs about random subjects. For example, the first album is about a man called Cerpin Taxt who overdoses on drugs and is in a coma, goes through a whole coma-odyssey-type-deal, and then at the end has to make the decision whether to die or stay alive. So you can't just base your opinion of them because they don't play straightforward music, or conversely, because every other hipster doofus likes them and you want to be cool.
It's like Pink Floyd's The Wall. You can't listen to one song on that, and you can't listen to the whole album without seeing the movie....