I thought I'd mention something many might consider a non-issue, irrelevant or just downright silly.
Two days ago I received the German-made
StageDiver 2 (SD2), which is a new custom IEM made universal. Now, I hadn't worn an IEM with a cable-over-the-ear fit for a long time (except those times I've worn my FAD 1601SS, whose ergonomics are less than stellar and, in my case, only by running the cables over my ears I can get to wear them).
So, for the last two days I've been using the SD2s. Been very, very hot at present in my neck of the woods for 1.5 months, so I'm finding, again, that an over-the-ear fit isn't great as the cables touch with my neck—my neck which sometimes gets a bit moist / sweaty due to the heat. With a cable-down fit the cable barely touches my skin, so I've just noticed how I've taken for granted that aspect of several IEMs I own. I have, in effect, got used to a cable-down fit with my favourite IEMs (K3003, Piano Forte IX, FI-BA-SS & Flat4-KAEDE), but here's the thing, the K3003 is the only IEM of those 4 that I can put in my ears and take them out literally instantly (with one hand), pretty much as fast as when you cover your eyes with your hands.
I know that the 'audiophile' thing is to have a cable-over-the-ear fit, which, of course, often helps with IEMs with microphonic cables (not the case with the K3003, PF IX, KAEDE & FI-BA-SS cables—the IE800, which I no longer own, has a terribly microphonic cable).
Like I said, perhaps quite a silly thing to talk about, but an aspect I personally value a quite a bit on my K3003s—or I value more these days. As time goes by, I've come to appreciate this IEM more and more; horribly expensive, yes, but to have an IEM that comes so close to my HD800s sonically, that is so comfortable (in my case, of course), with such ease of use, with no occlusion effect / bone conduction issues, that allows my ears to breathe (!) and, on top of that, that allows me to get pretty stunning SQ out of my 4G iPod Touch… no aftermarket cables, no portable amps and DACs, just these IEMs with their pretty small housings and my DAP: Absolutely brilliant!