Like the rest, it is the adventure aspect that I am excited about. Everything is so detailed and it just gives me the urge to explore a small area thoroughly, but at the same time it presses me into moving on and seeing what is out there. Along with the other mentioned mechanics that will be in the game, I am sure it will be impressive.
I want to be able to explore the amazing new biomes, interact with all the unique mobs, and do everything else adventure mode throws at me. I can see myself spending a lot of time in this just like I did with MC.