It's a great little adventurer that fits into the Zelda canon, with intuitive but clever puzzles that are for the most part challenging without being frustrating. It's got the trademark fun and humor inherent with the franchise (Princess Zelda is particularly a hoot).
I'll save my larger write-up for when I'm further into (or finishing) the game, but there are a couple of rocky spots in Hyrule.
First, I'm not all that thrilled with the train mechanic. It feels gimmicky, and while core to the story, I wonder if it was a good design choice, or maybe fast travel has ruined me and my patience.
Second, I dislike requiring the stylus to make a player move, because it gets in the way of being able to see what's happening on screen. I like having the D-pad as an option to move around the screen, and since there are (at least right now) unused buttons that could be assigned to the map and menu screens, using the D-pad for these functions (and requiring the stylus for movement) feel like forcing the DS mechanics for the sake of enforcing the DS mechanics.
Lastly (for now), the sketchy directional control of upgrades like the whirlwind are sucky at best, causing frustrating battle moments and required replays. Not fun.
But these are nits compared to the overall game, and that's why I call them out -- the whole game is great, so these shortcomings shouldn't be seen as taking away from the overall experience.
More later ....