This is my first review, so here goes:
There's few times when I finish a game and verbally say `wow'. Spirit Tracks is one of those games and I can honestly say it's the most fun I've had playing a Zelda game (or a DS game, for that matter). The game's presentation is pretty impressive and you'll find few games on the DS with as high production values.
The control scheme is incredibly intuitive and it'll take mere minutes to understand the basic mechanics. If you've played Phantom Hourglass you'll feel right at home here. Link is entirely controlled via the stylus, while either shoulder button will activate your secondary weapon. Don't worry if you're left handed; Nintendo has you covered here.
There are less main dungeons here than there are in previous games - 5 in fact. There's still a returnable dungeon like there is in Phantom Hourglass, but you're not required to visit previous floors, there's no time limit and utilizing the phantoms is actually part of the mechanics instead of avoiding them completely. However, having less dungeons isn't a problem at all because for what Spirit Tracks lacks in quantity it more than makes up in quality and passion. Spirit Tracks is a game that feels as if a lot of love and thought just went into. Often you might be left after solving a puzzle and end up thinking `How on earth did they think of that?' The boss fights are all impressive and utilize both the DS' screens and each one is more impressive than the last. The final boss fight sequence instantly became one of my favourite boss fights ever.
There's also hours worth of side quests to do, which will give you access to extra sections of tracks, allow you do customize your train, upgrade your shield and sword and even change Link's clothes. If you just want the collect treasure then you're also free to do that - which is where the mini-games come in. Spirit Tracks has five mini-games, all of which are completely different from each other and incredibly fun. Each one act as a means to gain useful items, treasure or just to pass the time.
The characters carry the same charm as they did in Phantom Hourglass and each town has its own unique qualities. There's no Linebeck like there was in Phantom Hourglass this time around though (who has arguably the best character in that game), but you do have Zelda tagging along with you instead. Spirit Tracks actually manages to make Zelda more than just a plot device and actually makes her into a fairly charming, likeable and entertaining character. She's also an integral part of the gameplay too.
The music - especially the overworld music (which you'll be hearing a lot) is incredibly well done. There's even the added touch of the train sounds actually syncing up with the music. If I had a top list of game themes, Spirit Track's overworld theme would pretty high on the list. It's incredibly catchy, gets you in the mood and you'll probably be whistling or humming along to it as you play. There's a few other songs in the game that stand out as well, such as the Goron Shooting Range theme.
Graphically, you're not really going to get any better on the DS. Spirit Track is a pretty gorgeous game considering it's on the DS and the only games that springs to mind with comparable graphics would be its predecessor and Avalon Code. This is a perfect example of why a stylised art and graphical direction are much better than trying to look realistic.
There are a few minor problems though, but they might only be a problem to the completionist. When you start a game, certain items from the treasure pool will become rare and incredibly hard for you to come by - probably to promote the trade system. This is a problem when collecting train parts since they all require a certain amount of treasure to purchase. There are workarounds to counter this, but they're still fairly time consuming. The rabbit catching fetch-quest can also a bit long and tedious, but not something to worry about unless you really want to go for a 100% save game or want your sword to shoot beams. There are also sections of slowdown while on the tracks when certain enemies appear in certain areas, though this isn't much of a problem.
So overall, I personally find this game to be the best handheld Zelda game available. While Link's Awakening and the Oracle games were amazing for their time, Spirit Tracks just brings everything to an entirely new level while still managing to introduce some new themes without falling on its face.
It's not your conventional Zelda game, and it's all the better because of it.