Note I didn't do the preorder for the earring, and didn't even know what it was good for, but then I saw the 30% XP boost below 70, and looked more closely.
Unfortunately, it only works for DOW, DOM classes, which makes it useless for leveling my crafter / gatherer classes.
I wish they had made it usable for all jobs. If it did, I might actually have a chance of catching up in my craft leveling..