I couldn't put it down last night and I played it until 4:30AM
Luckily I was able to finish the Dragon Roost Island sequence earlier than that. But I will say that it took an incredible amount of willpower to save the game and turn it off before leaving the island. I was so tempted to "just go see what the next island looks like"...
The "island" theme reminds me of the LucasArts Monkey Island games. That's probably part of why I like this game so much...
Regarding the "kiddie" thing: I have to say that so far, two of the islands (the first one and the third one) seemed far too kiddie for my tastes and I was teetering close to just letting my daughter finish the game. I'm glad I hung around long enough to get to the Dragon Roost sequence, it made it all worth it.
If I think about it, the Monkey Island games were kind of kiddie-looking all the way through. What made them so fun for me as an adult, I think, was the flavor of the humor. It was the kind of humor that catered to both adults and kids equally. There were enough "in" jokes and subtle twists that only the grownups would get.
I think that's something that's more or less missing from Windwaker: that subtle adult-sensibility humor. I'm sure that's largely due to the translation from Japanese. I'll bet there's all sorts of pop-culture references and tongue-in-cheek stuff that I'm just not getting because I'm not Japanese. So the eye candy and the quality of the puzzles is what really has to hold me for this game, and fortunately, it succeeds in spades.