I'd agree partly to that. The indicator of the problem with many audiophiles - even those, perhaps
especially those who do reviews - is for example that they can spend ages explaining jitter to you, then write up some review that's completely subjective without any real frame of reference. Most audiophile reviews qualify as stand-alone prose for that reason. There is no validity of opinion without consistency.
That aside, in the context of software it's not all about the sound but what you can do with the music, and how you can access it. For a musicphile, I'd say that - the versatility and ease of use in terms of actual practical usability of those things without frustration - is also as important. While it has decent usability for casual use, iTunes lags behind superior PC software in that respect, as does Front Row. It also extends beyond the immediate computer listening experience. You're more or less locked in to syncing with the iPod, so your only choice is with a non-market-leading (in terms of sound quality) player for example. And the way Front Row presents music in a home environment, while acceptable, leaves something to be desired when compared with some other (invariably Windows) solutions.
I don't think anyone is ultimately arguing that the OSX/iTunes setup is anything other than OK, in terms of sound coming out of it as much as anything else - it is perfectly usable for 'the average joe' as said before by others. But when you want more control over your music and how you listen to it as both a serious audiophile or musicphile might, that is when it lags behind.
That wouldn't be a bad thing if there were other superior options, since different people can opt for what they feel comfortable with - but there are no other real options, and that brings me back to what I've effectively said about three times already, that OS X is not a platform for musicphiles and audiophiles despite it being a perfectly viable music production platform. And in that way, it does indeed fail 'prosumers' and audiophiles.
...This attitude to iTunes some of you guys have really is like arguing for Bose
