Played Phantom Hourglass? If so, then you have also played this.
Before launching into a tirade, I'll get the pleasantries out of the way. Even though the series' stagnation is what most annoys me about it, what works here is what always has; the dungeons are all great. The new items are fun and, in tandem with the old ones, allow for some stimulating puzzles. Bosses are epic, usually taking up both screens of the DS and requiring clever use of the tool you've just acquired; the boomerang and bow bosses, in particular, stand out. The game is also clearly aware that you've taken the beginners course in using any items which make a return and throws new types of puzzles at you from the get-go. Finally, while not putting as much emphasis on the plot and characters as Twilight Princess did, Spirit Tracks does feature some humorous scenes which will have you smiling. In these regards, the game is a welcome step forward.
The transportation system, however, has taken about 3 steps back. In Phantom Hourglass, sailing worked. You wanted to go somewhere? You drew a line and off you went! Along with the cyclones for fast travel, this was pretty much a perfect set-up. Spirit Tracks' problem is in the title. Limiting your travel to set routes makes getting from place to place incredibly tedious; it often takes twice the amount of time that travelling in a straight line would and the fact that your train chugs along at a snail's pace doesn't help. The actual mechanics of it are largely the same as before - draw a line along the track to mark your route and tap anything to fire at it with your cannon. The only new additions are VCR style speed settings and a horn which is used for some miscellaneous events. The camera is just as awkward as it was and is made even more sluggish by noticeable slowdown when fending off larger groups of enemies - this is something which plagues other areas of the game too.
As if it doesn't already take long enough to get from place to place, the rails are often patrolled by enemy trains which will kill you on impact. This means you'll need to alter your route to avoid them, causing even more of a detour. Thankfully, there is once again a fast travel feature. You'll come across pairs of what can only be described as Stargates between which you may teleport. These do help, but nowhere near as much as they need to - it would have been far more beneficial for them to be totally interconnected rather than paired up. Again, this is a step back from what was previously available. If you were amongst those who found the sailing in Wind Waker and Phantom Hourglass laborious, it's safe to say you won't find any respite from it here.
That said, my primary concern is not with the train system itself. On the contrary, when simply sticking to the main quest, you won't have to do an enormous amount of travelling and what's there usually has some sort of puzzle or scripted battle to keep you occupied as you go. This game's problem is in its side quests. The mini-games and large-scale collection quests make a return but the bulk of the extras in Spirit Tracks come in two flavours: escort and delivery.
Escort quests, as you'd expect, involve transporting someone from one place to another. The problem here is that travelling with these people is like driving for Hyacinthe bloody Bucket. While escorting a passenger, you are required to obey the rules of the rail. Speed limits must be adhered to and when indicated you must toot your horn, enemies must be dealt with before they hit you and don't even think of overshooting the final destination by a centimetre or else you'll be on the receiving end of a scolding. Make enough mistakes and your passenger will get off the train and you'll need to start over. The good news is that this is all very easy to do. The bad news is that it's very very boring.*
Delivery quests are worse. On your travels you will find people in need of various trade goods. Once you've figured out where this commodity may be,** you go there, pay (!) to have your wagon loaded up with it and then bring it to the person who wants it. You are given a set quantity of the goods and the recipient will generally require either that exact amount or something very close to it. The problem here is that any enemy attacks incurred will result in a loss of cargo - one or two hits generally puts you below the amount you needed to deliver. Should this occur (and it will), you must go back, pay again and start all over. I didn't think it was possible to make fetch quests even more tedious than they already are, but here I stand, woefully corrected.
The rewards for all of this business are Force Gems, which reveal secret pieces of track throughout the world. These are usually short cuts,*** but a few unlock areas with extra mini-games and treasures. Perhaps the most annoying part of all this is that only one quest of each type may be undertaken at a time. As such, this creates a lot of back and forth drudgery which is about as stimulating as an actual train journey.
Touching on reality, Phantom Hourglass had a few instances where you were required to shout into your DS microphone. Something which made playing it in public areas a bit undesirable. This game, naturally, has even more of them. In fact, some of your items require you to blow on the screen to activate them. As well as making you look deranged, areas which invoke heavy use of them can make you light-headed! The software also seems to have advanced enough to recognize speech - certain bits will have you yelling CUTE, ARIES, or BROWN at your DS like some sort of crazed loony. As such, this isn't a game you'd generally want to play in the presence of other humans.****
You may have noticed that almost every point brought up thus far has been a comparison with Phantom Hourglass. That's because these two games are so ridiculously similar that it's very very hard not to compare them. They follow exactly the same format.***** The graphical style is identical and a lot of the music has been heard before, though the new additions are quite good. Most notably of all, the generic central dungeon has returned - stealth sections and all. Though, having ditched the awful time limit mechanic from before, it is much improved. The new gimmick here is that Princess Zelda's spirit (who serves as your Navi/Midna/King of Red Lions) can possess the phantoms which roam its halls. This allows for some co-op style gameplay in which Zelda's larger, stronger form grants you access to new areas and provides aid in solving puzzles. This is mostly quite fun, but the pathing AI can be frustratingly dim at times. If the Sisyphean nature of Phantom Hourglass' core dungeon was what put you off that game, this one might be worth a look as it does improve much of what was wrong with it.
This may have read like a slating, but the reason for the large amount of criticism is simply because Spirit Tracks does very little that we haven't already seen. It is essentially Phantom Hourglass, with boat swapped for train. While the dungeons, bosses and puzzles are as good as they always are in these games, the train system feels like a massive step backwards and the majority of the side quests are simply not fun at all. If you weren't impressed by Phantom Hourglass (or any other Zelda game), this isn't likely to change your mind but if you're new to the series and trying to decide on one to start with, it's as good an introduction to it as any.
* Ever tried blending in with the rest of the traffic in GTA for a laugh? Yeah, it's like that, except without the laugh.
** Not particularly hard to do as pretty much every inhabited area has some sort of speciality.
*** Which may make your next escort or delivery slightly less boring than the one you just completed.
**** Or particularly cool animals.
***** As opposed to other Zelda games which simply follow the same format.