It's not so much the sound in my case (5G superiority being borderline testicles in an everyday listening sense) but the UI. The 6G just bogs down with every navigation request and the more basic UI / metadata reading of the 5G was definitely more responsive - and that's a huge part of the iPod experience IMO. I just don't pick up my Classic anywhere as often as I used to the 5G mainly because of this reason. I'd love to put a bigger HDD in my Classic (my library is currently <110Gb for just for the compressed audio, so that's what the Classic contains) but if it's as jerky an interface experience as it is now - forget it.