The Legend of Zelda: The Wind Waker HD is going to be different for its HD-ness, but there are plenty of other changes, too. We came across a really nice list of all the changes known (outside the graphical ones) so far for the game on NeoGAF today.
We'll have you head over there for the full list, but there are some pretty interesting changes worth noting. Apparently, pulling items from the sea floor is now four times faster than in the original. You can also now move in first-person view when aiming.
Little things make a difference, like being able to switch camera controls, or a slightly faster text speed. There are a lot of small changes like this as well.