http://www.wowhead.com/?item=43367 + http://www.wowhead.com/?item=41108
The Glyph of Divinity will cause your Lay on Hands, when cast on yourself, to give you twice the mana back of a normal Lay on Hands. The +20% from the Glyph of Lay on Hands does not apply to the Glyph of Divinity return, when used on yourself or another person.
In short, 16-20 minute cooldown, restores 4290 mana when used on yourself. Worthwhile for Prot? Holy? Ret? What does the paladin community think? An extra mana potion in emergencies?