I've talked to several Japanese gamers who own The Legend of Zelda: The Wind Waker, as well as many people who have imported it, so I have a pretty good idea of what to expect from the game.
This is basically spoiler free, although I do go into a small amount of detail about game play elements (such as the music, graphics, control, etc.). So if you don't want any of that stuff spoiled for you, then I suggest you don't read.
The story, I hear, is pretty good, especially for a Zelda game. I won't go into detail about that, but you won't be disappointed.
The game controls very much like Ocarina of Time and Majora's Mask. There's a targeting feature, and Link has his backflips and side jumps and everything like that. He has a few new stealth moves, but from what I hear they're pretty much only for show and don't really accomplish much. There a new move that allows you to counter-attack if you press the attack button at a certain time, and that sounds pretty cool. Also, the music changes depending on what's happening in the battle, so that's cool too.
The difficulty of the game ... well, from what I hear, it's pretty easy. There are a few parts that are tedious (just like there were tedious parts in Super Mario Sunshine), but other than that, it's easy. Probably a little bit harder than Ocarina of Time (which means you can't play this one in your sleep, sorry), but not nearly as difficult as Master Quest. If you're looking for a challenge, go elsewhere ...
... But if you're looking for a great experience, Zelda has it. Most people I've talked to have had a great experience with the game. Most give it a 10/10.
And now, the most controversial part ... the graphics. Despite all the whining that most people did, the people who actually own the game say that the graphics are beautiful and satisfying. So I suggest that all the nay-sayers shut their mouths until they experience the game for themselves.
So all in all, it seems like we got a pretty good Zelda game on our hands. I'm glad, too ... the first Nintendo 64 game scared me about the direction of the series a little. Luckily Majora's Mask and the Oracle games pulled through, and it looks like Wind Waker just might, as well.
Remember, the game comes to the US at the end of March ... go get it.