This is covering my personal experience with the librams, if you have anything to add or comment on feel free to post.
most important detail to note about librams is higher ilvl does not mean its better.
ilvl 264 Libram of Blinding Light
"Your Holy Shock heals grant 85 spell power for 15 sec. Stacks up to 3 times."
this is usually laughed at and mocked by pallys as junk. often because no one spams holy shock (not very mana efficient and other reasons) to keep the proc up all the time. and even then, increased sp on holy light is usually just more overheal and if your looking for increased sp on flash of light then that's what the pvp libram is for. main use for this libram is GS boosting in dal if you like doing that with items you never use.
ilvl 245 Libram of Veracity
"Each time you cast Holy Light, you have a chance to gain 234 spell power for 15 sec."
good for fights with a decent amount of holy light and flash of light mix but not so much that you will have mana issues. very fine line however because crit holy light with extra sp often just leads to more overhealing so pvp libram may still be a better choice (except that this will also boost holy shock). i always just take ilvl 200 one if i know i'm going to be holy lighting a lot.
This is also the best libram to use during the Dreamwalker encounter for healing her since you will have infinite mana an no overheals.
ilvl 232/251/270 'Title' Gladiator's Libram of Justice
"Increases spell power of Flash of Light by 375/436/510."
excellent for healing heroics and often pre toc raids where pure flash of light spam (with toc/icc gear) will get the job done.
you will need an arena team score to get anything better then the ilvl 232 (375sp) version of this
ilvl 213/226 Libram of Tolerance/Resolute
"Increases spell power of Holy Light by 141/160"
Simple static holy light boost, this libram is really not even worth mentioning as the ilvl 245 libram is a direct upgrade.
ilvl 200 Libram of Renewal
"Reduces the mana cost of Holy Light by 113."
don't knock the ilvl of this libram because its still the best choice libram for raiding, especially fights with continuous holy light spam.
some fights I've seen up to 120 holy lights easily, which comes to almost 13k mana saved.
even if your mana pool is double that of what people had in naxx when this libram was first out, this is still your best choice libram unless your just spamming flash of light in something easy like pre toc raid or heroic dungeon.
Also dont be ashamed to wear this libram around in dal due to its lower gs. i'd rather look like i know what i'm doing with this libram then look like an inexperienced player with the 245/264 libram on in dal