Ideal vs. suboptimal piano tuning: it DOES matter!
Piano tuning is an art demanding not only precise hearing and listenening but also mastering a set of hand skills. Unfortunately, there are piano tuners who all too often either do not take their job seriously or are not up to the task. Similarly, the opinion of some customers is that an ideal piano tuning is not really important because they "can't hear the difference anyway."
The latter point is a falsehood with potentially far-reaching consequences, particularly when children play the piano. Children react sensitively to the result of their efforts at the keyboard, and their motivation to play the instrument depends heavily upon how the sound excites or frustrates them. These young musicians, as well as most musically active adults, are not able to dissect the overall sound of the instrument in order to name the individual factors that they dislike – they experience the sound as a whole. When it sounds "good," it increases motivation to play and practice; when the sound is not so appealing, children and adult musicians react negatively and, with time, lose enjoyment playing the instrument. Of course, the choice of appropriate music in the child's practice repetoire is also a factor in motivation - I simply wish to point out that regardless of music choice, the tuning of the instrument (good or bad) is of paramount importance.
All compositions, even the most simple, are based upon the musical ideas of the composer. When composing harmony in music, the composer has an inner, mental sound impression of a "well-tempered" (i.e. ideally tuned) piano, or perhaps there even is an actual well-tempered piano within reach. The more a piano is out of tune, the less one can hear the original intention of the composer. There are chords and intervals which sound truly repellent when a piano is very much out of tune, but even being slightly out of tune causes harmonies with subtle or characteristic sounds to lose their effect.
To experience a composition in its full, intended beauty - thus retaining and even increasing enjoyment while playing - an ideal piano tuning is absolutely necessary.