On the subject of GG, don't you only get -2 for higher level kills?
Yup, no different than picking up a pile of gold
Is anyone a fan of the late-game boons? - they seem a tad too general - I can't really see what character gets any particular advantage from either of them, especially given the high piety requirements.
Enlightenment is a false path; don't even consider it unless you've got Pactmaker for consensus to get out. Protection is alright, but not worth sacrificing your potions. Unless you're going for parched, always convert out.
As I've said before, there are two types of GG worshipper: the early worshipper and the late worshipper. Early birds want to get in no later than level 3, grab humility and absolution, then convert out at their first convenience (new piety gain structure means you can linger up until it's time to use your potions). Unless you've got an emergency, don't use protection. The late-worshipper converts in after drinking all his potions, then uses his piety for protection and ignores humility and absolution. There's nothing stopping a former early worshipper from converting back to become a late-worshipper, but generally there is no overlap between these two approaches.