First, I want to talk about the most controversial aspect: the trains. Personally, I love the trains. The game's world is made up of several different areas which are all connected by a large railway system. This completely changes the way you travel across Hyrule and I find it quite refreshing. You use the touch screen to tap things you want to shoot with the train's cannon or to pull a rope to blow the whistle (which you occasionally need to do). There are some little boss battles that you do while in the train and sometimes you need to use it to deliver goods or to give people lifts between different destinations. Something about driving these trains is hugely satisfying. The only problem with the trains is that they aren't used often enough. I hope a future game will make use of them.
Another new exciting feature is the addition of Zelda as a semi-playable companion with Link. Near the start of the game Zelda is essentially killed and is left as a ghost. As a ghost Zelda can possess big phantom enemies which are then required to solve certain puzzles. The whole game is controlled with the DS touch screen, however, and I feel this makes this mechanic a little needlessly difficult.
The game also makes use of the DS microphone and this is another way that I feel the game has been hindered by its need to use controls other than buttons. This time Link has a musical instrument again (a pan flute) and to play it, you move it around on the screen while blowing into the microphone. Usually, this is fine, but sometimes it just didn't seem to work at all. Twice I actually started to feel lightheaded because I had to blow into the microphone so much (since it just wasn't working.)
I also feel the game is let down by its dungeons and storyline, which both felt a bit 'generic Zelda'. Link is a regular guy training to be a train driver, when he gets caught up in the events that leave Zelda as a spirit, so he has to help collect certain items so he can help defeat the evil that caused this, and so on. The villain, by the way, felt to me like a poor stand in for Ganon. The dungeons, meanwhile, never felt like something new.
But don't get me wrong, this is a good game. It moves the series forward in ways that I like a lot, but I feel that it was held back by its need to maintain certain staples of the Zelda series... Staples that are not necessarily bad, but which feel rather unoriginal here. It's the good things, however, that I remember fondly; a more prominent role for Zelda (with some lovely interactions with Link) and an absolutely wonderful new train feature. Rating: 8.9/10