I am not who you were responding to, but I noticed some of the same thing. With certain tracks, the voices would be a bit piercing, and trables, especially cymbals would start to sound distorted and ringing like the other poster said. Mostly with rock/alternative tracks where the drums and cymbals are more forward in the mix combined with a lot of electric guitars.
I am not a big believer in burn in, with the exception of maybe brain burn in and adjusting to the sound, but after a few days they definitely seemed to ease up a bit. I also have found that using dampened filters helps, and I am now trying kombi tips, which also seem to be helping a bit for me as well.
Its kind of a shame about those because a lot of tracks sound really great.