



Not a good idea to tune to the 12th fret. The farther up the neck you go, the least accurate your intonation becomes. I could see doing that as a reference to a guitar that's properly tuned but never as the focal point of your tuning.
I've done this when cutting tracks for solos. I've also done it to adjust intonation when setting up new guitars.
Tuning on the 12th doesn't make much sense for onstage tuning, though.