I'm pretty excited. The minibiomes and NPC interactions are what have drawn my attention most. I've just recently started building my complexes into more "realistic" forms (giving NPCs rooms separate their work rooms, more that just 1 or 2 beds, a tavern to eat and drink). Having my NPCs actually use the furniture or go to sleep at night would be really cool.
I hope to see more food items added to terraria. It'd just be nice to add a bit of diversity.