It seems odd to me that such a mellow instrument as the acoustic guitar has to be tempered.
Now, the trumpet, you'd think would be far more tempermental ... and yet I tell my cousin (whenever he disses the trumpet) that it's a perfectly tuned instrument, unlike all his stringed thingies (like gutiars, pianos, sarods and banjos and etc.), which are totally tempered (like he needs to be sometimes).
I've alwasy found it interesting (confusing really) how fret spacings can be radically different and still in tune, like the difference between a jazz bass and one of those really short necked ones .... can't remember what they're called by Fender. Both have good intonation. This Eastman (E20 OM) is exceptionally well in tune up and down the neck, but I don't know why it's better than most guitars I've had (including Martins).