Wow, really? Because tuning an electric instrument by ear is MASSIVELY easy. You just play the harmonic above the 4th fret on the lower string, play the 6th on the higher string, and tune the higher string until the woowowowowowowow sound becomes woooooooooooo. Hah, come to think of it I got dudes pissed at me on another board because a dude was beginning to play guitar and I told him he should learn how to do this instead of tuning every string to a tuner. I still say I am right!
Tuning with harmonics will put you out of tune
slightly--and you will compound this when you tune the subsequent string.
Harmonics would work if we were using the "just intonation" or "pythogorean tuning" but we don't.
We use "Equal temperament", so those harmonics on the 7th fret are slightly out of tune. (equal temperament makes the distance between all half-tones equal, so one can play in all keys)
The best bet is to tune with fretted
notes, a pitch pipe or a tuner.
One of the reasons for the use "power chords" when using distortion is that distortion increases the sound of certain overtones--and the one the correlates to the 3rd is out of tune and will clash with a fretted third, so it is best to omit the third.