Alright, just had some hands on experience with OoT 3DS as well as other things, but we'll focus on Zelda on this site, shall we?
Firstly, the 3D is gorgeous, particularly gorgeous due to the greater lighting in the game compared to the other 3DS games. There is a very discernable 3D image of Link, and of objects slightly behind him, and the background even further behind him. This in effect gives it about 3 distinct layers which adds tonnes of depth. A particularly nice 3D effect is to watch Link backflip at you, which has been redesigned now so it's slower and slightly more dramatic. Also, the "sweetspot" where everything looks just right and doesn't go blurry, for me, was with the 3D slider at about 2/3 on, and looking directly at the console. It's also fairly easy to contain the console at that sweetspot, unlike Kid Icarus, which was more demanding. Backgrounds have been completely remodelled in this game, also adding to the 3D effect as no longer was it blatantly evident that the backdrops were 2D images imposed as walls in a 3D game. Textures have also been dramatically upgraded, from the green of Link's tunics, to the ground, to the vines he climbs (I might add he can climb slightly faster now which is always a plus) and these become immediately obvious and really refreshes the game.
The controls play very smoothly, the slide pad is a worthy replacement of the joystick, L-Targetting works great too, the touch screen is very responsive and the gyroscopic controls work a treat as well, allowing you to look around a room with 1-1 motion controls as well as aim the slingshot and presumably the bow too.
In terms of content, nothing I could see has been changed. Dialogue is identical to the first (except for basic control tutorials given by the Kokiri) as far as the demo goes. But they did block off the Lost Woods in the Kokiri Forest, but this, once again, may be just for the demo. Dungeon layout is the same, as is the internals of buildings, so far, it looks like it's just the original with a dramatic facelift and slight redesign of minor details. But overall, it's faithful to the original, and has so far not taken a misstep in execution. If the final product is anything like this, it would be a worthy tribute of the masterful game.