So far my fav thing is the map. Im looking forward to what it's really gonna look like! And being mayor! And building placement! Yay!
most of all I like that you can finally hang stuff on your walls!
I love every single feature coming to the 3DS! But, my favourite feature would have to be the almost "unlimited" customization of the town. And building buildings where you want, it's great having everything where you want it, and looks as you imagined it. :]