Ok, extremely early impressions based on about 30 minutes of play.
Bad:
1) Aliasing everywhere, really bad, especially in the first area with so much grass.
2) On top of aliasing, the image is really soft, so you have the double whammy of a soft-blurry image that you'd get from post processing, but none of the benefits of anti-aliasing. It's not even close to the prettiest game I've ever seen on the Wii U.
3) Frame drops around any grass, when panning camera many times, or when fighting more than a couple of enemies.
4) I'm already over item durability. Limited weapon inventory space combined with weapons that break in a couple of fights isn't fun. I've also run into an area where it's too cold to enter and peppers I have to cook to keep my body temperature up, so this combined with other things I've read seems to point to this game having many, many gimmicks that may not be fun gameplay.
Good:
1) Huge open world, you can go anywhere, climb anything, it's pretty much choose your own adventure. Right out of the gate they kinda point you in a direction and that's it. I never even hit the first place I was supposed to go due to exploring.
2) Difficulty. I didn't even check if there is a difficulty slider, but I got one shot by some blue Bokoblin not far from where the game starts. It's not dark souls stuff, but it's already harder than any Zelda game I can remember in a while.
3) Little touches like walking around outside a building will cause enemies to hear you and patrol. If they see you they will call reinforcements. I even had one guy blow a horn to call in all this buddies. I took an exploding barrel and threw it near other barrels and made a giant explosion that blew a bunch of enemies up, it was pretty cool. Another time I was fighting enemies near trees and hit the tree and put chop marks in it, a couple more swings and I chopped down the tree. You can also climb trees to pick fruit, etc. It seems the world is really interactive overall.
4) The game is 100% playable on the Pro controller, the gamepad literally does nothing which is just fine with me.
Overall haven't really gotten a lot done, I've fought about a dozen creatures, found a few chests with some clothes in them and found a gated area I need warmer clothes or something to enter without freezing. It's been fun even with the frame drops and shitty graphics.