I can't speak for 
@EzekielRaiden, but for me, it would depend on how much leeway I'm allowed.  If it's just "make up some holy days and ritual practices", that's not really a ton of input.  Can I make up a holy order?  Can I have input into their beliefs?  Can I tweak the alignment, like say this LG god is really more LN?
Like, it's pretty core to me that I play a character that's 
my idea, not the GM's idea.  I generally don't want the GM to make a setting that has PC concept-shaped holes that I'm expected to fill as a player.