I want to point out beforehand that I have perfect hearing, don't listen to loud music, no history of ear problems, etc. I'm still a teenager also, so my hearing should be better for that fact.
Anyways, I have tested this on my Computer + Asus Xonar STX and iPhone -> FiiO E11 using both the Monster Miles Davis Tribute, Monster Turbine Pro Gold, Beyer DT770, and Beyer DT990.
I failed around half of the blind AB tests, and honestly could not find a difference. I have had multiple friends who has tried this also, and they only did slightly better, if not the same as I did. I know I don't have the best gear in the world, but certainly, shouldn't differentiating 128 and 320 in blind tests be 100% easily? I tested on several volumes, different times of the day, and even in the dark (It enhances hearing a bit, really.)
Especially since most of the "OMG 128 is garbage" comes from people who have similar if not inferior gear to me. Even the cymbals, which some claim to be "painfully bad" on 128, can only be differentiated by playing the specific part repeatedly on both mp3 clips. My music selection was mostly Lincoln Park with some Adele, using CD Ripped 320 and online downloaded 128.
Can someone explain this? Because this is clearly not a night and day difference, even for a couple teenagers who have perfectly fine hearing.