Warning: Some moderate spoilers about the gameplay follow.
It's quite hard to form an opinion on this game. In some ways it's quite superb, in others, it's quite strange.
This is an RPG by Square/Enix, but it's a rather different type than the typical Japanese RPG by that company. It's also different from typical western AD&D-style RPGs. It's almost like an RPG genre of its own.
Many of the "minus" points are not really all that negative. They are more like borderline cases. The game is just so difficult to judge in so many areas...
Very good 2D graphics. (At places they get a bit too blurry because of zooming, though.)
The battle system is innovative and superb. Instead of being a strictly turn-based battle system, like in most other Japanese RPGs, in this game attacks can be launched simultaneously or in quick succession (ie. another character can start attacking while the first character is still doing so). This allows creating combo attacks. The battle system rewards massive combo attacks by offering special attacks which a selected character can launch (and if this special attack fills up the combo attack gauge enough, a second character can launch a special attack, and so on).
There are lots of stats, traits, skills and special moves which can be optionally improved when leveling up. In most Japanese RPG games all stats are incremented and new skills/spells are learnt automatically when the character levels up, but in this game the character receives capacity points when it levels up, and the player can distribute these capacity points among a long list of stats and skills as he chooses. It's almost like the exp mechanism in some western RPGs (even though the character only receives a predetermined amount of points per level).
Regardless of the negative points described below, it has still succeeded in making me play all-nighters because of its addictivity. It's difficult to express what exactly is it that makes it so addictive.
Most Japanese 2D RPG games use an orthogonal projection of the world, villages and houses, viewed from an aerial perspective. This means that the scene geometry is located on a 2D ground plane, and the scene can be explored freely. This works very well.
For one reason or another, however, they decided to make this game a side-scrolling platformer, effectively making it a 1D game with platforms. While the implementation is actually pretty good (it avoids most, although not all, of the illogicalities of side-scrolling platformers), it's still a bit of a disappointment, as there isn't so much freedom of exploration, which is one of the major assets of RPG games.
In fact, this game doesn't seem to be about exploring almost at all. Dungeons have a small degree of exploration element to them, but that's about it. There's no exploration element for the outworld nor for the villages. In typical Japanese RPG games you explore the outworld and try to find villages or cities, and then you explore them, talk to people, get clues, buy things, sell things, etc. There's nothing of this in this game. (You can talk to people, but all they say is completely irrelevant.)
The most puzzling thing about this game, though, is that it seems to completely lack a main plot. All RPGs, be it Japanese-style or AD&D-style, have a main plot. It's this main plot that drives the game. The player has to follow the main plot, and solve puzzles to advance this main plot. While there may be sidequests, advancing the main plot is what advances the game. Most RPGs have very strong and involved main plots. Basically the main plot is what makes an RPG.
This game, however, seems to completely lack a main plot. Moreover, while it has very deep and involved small sideplots, these seem to be completely irrelevant with regard to the gameplay. They are a bit like mini-movies which you can watch but which do not really affect the gameplay in any way, don't give clues about anything nor help you in any way to advance in the game. Even the intro, which takes over an hour to play through (!) is quite involved but, in the end, seems also completely irrelevant with regard to the game itself.
The game seems to lack any sort of tutorial-style introduction, or some other clear indication of what is the goal of the game. Since the game and its goals are rather different than in any other RPG game, this makes the game rather confusing at first. Especially given that the amount of village/dungeon visits is limited, a new player will find himself wasting the valuable visits for nothing because he doesn't really know what is it really that he's supposed to do. It takes time before you get the idea of what you have to do, and by that time you have already wasted quite a lot of visits.
The "good end" of the game, that is, the ending which shows the actual intended ending of the story (which started in the hour-long intro) is basically an easter egg which is practically impossible to find out without reading precise instructions. The "normal ending", the one which you get by normal play, is little more than a "congratulations" screen (in other words, it's not the actual ending of the story).
The strange thing is that the game gives absolutely no hints that there actually is a different "good ending" at all. Also, it doesn't give any hints whatsoever about how you could get to that ending. The method by which you get there is very complicated and requires very precise steps to be taken at very precise moments in the game. Even if you knew there was a better ending (which you don't) it would be impossible to figure out how to get there. The only way to do it is to read meticulous instructions from the internet. It's basically a very well hidden easter egg. I find this rather puzzling.
All these negative points probably sound a lot more negative than they really are, though. The game is not as bad as it may sound and, as I mentioned, it can be quite addictive. I just have very hard time deciding whether this is an absolutely superb game, or whether it's a small disappointment.