The "hidden", as in there is no quest marker, scavenger hunt through Northwind was a really nice touch. Reminded me of a guild event in wrath where people organized one across the whole world for our guild, even with an enacted escort quest. Would like to see more stuff like that.
In general Northwind was really nice if you read the quest texts, though it feels a bit directionless in the beginning due to the quests being strewn out. Still pretty impressed with it.
Looking forward to Balor now.