The combat.
At first I was really reluctant because some idiot rep said the enemies were also "puzzles", but the more I see of the game the more wrong I think he was. The enemies and combat look to be reminiscent of 2D Zeldas like Adventure of Link and Link to the Past, not like a puzzle at all, but pure, fun combat (which is, to me, what was completely missing from 3D Zelda besides OoT).
Still I do't know, maybe the rep's right and we're really going to see "puzzle" enemies who are nothing like Girihariribirim. We did see a couple in the first trailer, after all.
There are also multiple other things which, depending on how they are made, could either be really awesome or really lame, like being able to upgrade your gear (if it's mandatory and required for puzzles, that would be... no different from past Zeldas, but if it's like LttP's upgrades, then awesome).