In a recent post here, Agitato mentioned the "pain" he experiences in listening to sampled orchestral instrument MIDI mockups such as those often posted in this forum. From what he says about his long-term listening habits (which seem similar to my own), I don't doubt that his ears are naturally well attuned to orchestral intonation. But MIDI mockups all apply a very different intonation schema - equal temperament - and that can be very problematical.
No matter how meticulously and beautifully the sampling and editing of orchestral instruments has been, even our very best sample libraries introduce the mostly fictional manifestation of orchestral musicians playing in equal temperament. I suspect this is at least one strong source of the "pain" reported by Agitato. I also tend to be somewhat averse to listening to MIDI mockups that use orchestral instrument samples, though I'd label the untoward aspects of my listening experiences as bothersome, irksome or even repulsive, rather than painful.
And there's another possibly significant factor. Of the great composers whose finest works populate the vast majority of long-term repertoires of western orchestras, only a small proportion of them have written great and widely-loved works for piano. Why might this be? Is it not because the 12 notes of equal temperament offer the composer far less scope for musical expression and far too much scope for unwelcome ambiguity and misperception in conveying sophisticated and subtle affective nuances to the listener? At the very least it seems reasonable to conclude that writing a fine and successful classical piece for piano is more difficult and demanding than writing for orchestral instruments. And here we're talking about the great composers. So now follows the uncomfortable point:-
How many music-makers today, equipped with expensive and well made sample libraries of orchestral instruments, can reasonably expect to write great orchestral music in the form of a MIDI mockup which, from the standpoint of intonation, might as well be a piano (or organ, or synthesiser)?
So it could be said that - paradoxically - equal temperament sets the bar too high for all but a few geniuses of piano composition. The result? All to often it's a "painful" or "irksome" experience for listeners such as Agitato, me, and others whose ears are attuned to orchestral intonation. I for one never listen to MIDI mockups written for small ensembles of orchestral instruments, such as string quartets, etc. I know from experience the likelihood that the highly sophisticated "real" intonation - including the many precise and deliberate unwritten modifications made in real life by musicians to the pitch of written notes whilst playing in ensemble - will be mangled into the travesties of music we call MIDI mockups.
But no doubt we'll carry on regardless, making MIDI mockups that few if any will fully enjoy - let alone love and cherish for years. Currently we have little if any choice but to ignore the elephant in the room.