I've recently left the armed forces where I had my hearing tested every six months. My left ear beats the test hands-down while my right ear struggles to pick up the very highest frequencies at the lowest volume in the test. All in all, my hearing was described as "almost perfect". I find my 80gb Classic to be a little on the quiet side when using over-ear headphones (Denon AHD1001). With my Denon C551's it's better but I can still hear ambient noise, especially onboard aircraft, and I fly a lot.
I think the better your hearing, the more chance you'll find them to be too quiet, purely because you'll be able to hear the ambient noise more readily than someone you who has less sensitive ears. The fact you can hear ambient noise over the music "tricks" your mind into thinking that the music is less loud.
My son has an IPod Touch and it is much louder especially with the over-ear cans. If I remember correctly, Gopod aren't around any more and therefore have not updated their software to include the recent iterations of the classic. I'm going to buy a Fiio E1 headphone amp instead. £15 well spent, apparently.