I've got a healthy dose of skepticism about my ears and the acoustic acuity thereof. This comes from a generalized transition that I had to make that, while I'm perhaps smarter than your average guy on the street, I'm probably not some Übermensch and always need to make sure that I'm not engaging in endless self-aggrandizing without some degree of justification.
I get my hearing checked on a semi-regular basis. It does turn out that if they catch certain kinds of hearing problems sooner rather than later they have a better chance of rescuing more of your hearing. Last I checked, it's pretty good. I can still hear The Mosquito tone, which is a 17.4 kHz tone that I'm not supposed to be able to hear anymore.
I suspect that at least part of this is because my brain's never been wired quite right. When I was younger, I had sensory integration issues, which meant that when the monthly mandatory air-raid siren test went off, I would be cowering with my ears covered while everybody else was going along like nothing happened. I'm better now, but this probably meant that I was exposing myself to far less environmental noise than your average part of the population.... and there's some research that suggests that we're overstating the role of aging in hearing loss because most everybody experiences a lot of hearing damage.
I know I don't have perfect pitch. Far from it. I'm pretty bad at picking out if something sounds sharper or flatter than concert pitch.
I've also noticed that I sometimes have a hard time understanding when people talk to me, despite there being nothing wrong with my hearing. I've started to suspect that this is similar to what happens with car buffs or train spotters. They've done some studies on these populations and found that they did correspondingly better at recognizing cars and worse at recognizing faces. I'm starting to suspect that this is what's happened to the auditory center of my brain. I can pick out what combination of instruments, doubletracking, delays, effects, etc. from a mixed song with great ease. I just can't make out the words on a noisy conference line.
I've been sorting through my musical collection and I've noticed some interesting things. First, I can hear the loudness war play out as I've merged and organized my collection. I've got a few incidents where I've got two copies of the same track on different albums (say, the original issue and the "Greatest hits" anthology) and you can hear that one's been cranked. This isn't always in chronological order. For example, Time3 by Journey has been mastered far quieter than their Greatest Hits, even though the Greatest Hits came first.
I decided that, since I've got a giant hard drive to play with, I can afford the increase in storage space to rip my music in FLAC format. And, after testing a few tracks to make sure that everything ripped right, I noticed that the track I was listening to (Dreams in Digital by Orgy) was much more lively than I remember. There was these high-frequency scintillations that sounded totally different than I'd remember. So I dug up an MP3 of it and listened. It sounded different. I even ripped it at a fairly high quality setting and it sounded different.
Now, given that I could readily hear the difference between MP3 and FLAC on my not-especially-impressive speaker set, I got curious about 96 kHz/24 bit recording. Now, the role of 24 bit recording in the audio marketplace is not just about audiophile purity. It's really about having enough headroom in the right places so that you don't need outboard gear while recording.
The problem, of course, is that the marketplace has exclaimed quite clearly that the 128k MP3 format is quite good enough. And both SACD and DVD-Audio were taken as opportunities to inflict further DRM upon the world, I've only really got one studio-quality set of 96/24 audio files... the Nine Inch Nails release. And, honestly, I can't tell much of a difference between the normal-resolution version and the 96/24 version.
I think my present working theory is that the people who make a big deal about 96/24 files are imagining things and that my hearing is, in fact, pretty decent. I could be wrong, but that's my present assumption.