This whole discussion is fascinating to me. I don't have perfect pitch, but I have a question for those who do. In studying musical scales, instrument tuning, etc, I learned that there is a mathematical "irregularity" in the diatonic scale we commonly use in western music (maybe other scales too - I'm not sure about that) because of something called the "Pythagorean comma". A detailed explanation of it would be too complex to attempt to give here, but the effect of it is that, in order for different instruments to play together and to play in different keys, the tuning we actually use is a compromise called "even-tempered tuning", which is deliberately offset very slightly from "perfect" tuning.

For example, the frequency ratio corresponding to a perfect fifth interval is exactly 1.5. In other words, if an A is 440 Hz, the perfect fifth above it (E) would have a frequency of 660 Hz. At first impulse, it would appear that one could tune a piano perfectly by tuning one note to a reference such as a tuning fork, then sequentially tuning the other notes in perfect fifths and perfect octaves. However, if you actually do this you end up with a piano which is badly out of tune with itself. To compensate for this, piano tuners don't use the ratio of 1.5 for the fifth - they use a ratio very slightly less, about 1.4983, or to be exact, 2 to the power of 7/12.

The thrust of all this is that it is impossible to achieve truly perfect tuning on a piano, most wind instruments, or on fretted stringed instruments. You can tinker with the tuning on your guitar until one chord sounds perfect, then when you change chords, it will be out of tune to some extent, hopefully not enough to be irritating. String ensembles (unfretted instruments) and a capella singing groups (e.g. barbershop quartets) avoid this problem, because they are not confined to the even-tempered scale and can make tiny adjustments in pitch as needed to produce truly perfect close harmony, at least in theory.

Well, never mind all that. My question for those who have perfect pitch is: Does the compromise of even-tempered tuning cause problems for you when tuning an instrument, or when listening to an instrument or group of instruments, even though the players may have just gone through a meticulous tuning ritual, using the most modern electronic tuners available?