Just finished it the other day. I wrote a review for gamespot so instead of retyping that I'll just copy and paste:
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All in all I have to say this is yet another stellar Zelda game. Featuring some of the best level designs I've seen in a long while! Some of the last floors of the Spirit Tower are masterfully designed and fiendishly tricky. Again wonderful music and character design as always and a compelling story. If you played the previous DS Zelda title The Phantom Hourglass you will know exactly what to expect here. In fact if you've played the previous one you may find this one too similar. Instead of a boat you run a train and most of the rest remains unaltered. But this isn't a bad thing in my mind. There's just enough new here to keep things from going stale and they have luckily removed the annoying amount of backtracking that was in the previous title. Like before there are also plenty of minigames, puzzles, battles, and side quests to keep you playing. Collecting all the different train types will take you quite a long time! The pan flute mechanic where you use the DS mic to actually play the instrument is really nicely done, it's just like the recorder app on the iPhone . There are a few minor issues that make it hard to copy the tunes correctly but nothing serious. My only real complaint here is that the final Boss battle with Maladus is far too easy. They should have invited some of the brilliant level designers in on the design of the final fight because compared to the innovative puzzles and boss battles elsewhere the ending feels rather plain. They should have incorporated many more of Links weapons into this fight. Instead you basically just have to swing your sword a bunch.
Still I highly recommend this game to anyone, especially Zelda fans!!
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Again, if you just finished playing The Phantom Hourglass not long ago the two games may seem too similar as there are a lot of similarities between the 2 games. But this is still more than worth picking up, just try to forget the similarities and let the story and level design suck you in!