Something that has been bugging me and I haven't seen it discussed much since Ghost Story:
Are we supposed to have figured out who said, "Hush now" and was it in response to the "Die alone!" death curse? 
I would also like to hear other people's ideas on this.  I remember possibilities being: Harry's mother, Lash, Mab, & Leah.  For some reason I'm leaning toward Lash.