Kingdom Hearts + Multiplayer
As with the other Kingdom Hearts games, 358/2 attempts to teach the players about the flavor of kingdom hearts and what the story and controls are all about. Considering this game is relatively dependent on the events of Kingdom Hearts 2, it would help the less informed to look up some of the events. I believe it is for this crowd that the lengthy tutorials exist in these games: it has an incredibly deep system and story.
Game play in this entry is similar to that of the other Kingdom Hearts games for consoles, with one noticeable twist: an immersive, customizable "panel system" that allows for players to customize characters as they play them. Within the story mode, your strategy may or may not change as much, and that is why there is a feature that allows you to save and quickly change saved builds on the fly. However, it is the multi-player where this really shines.
In the mission section of the game, which allows for up to 4 players (can can be still played solo) to attempt missions as any of the 14 characters. Within the realm of Organization 13, all of Roxas' stats are average, however nearly every other character has some defining trait that players will want to utilize to the maximum through the panel system. This, I find, is the "icing on the cake" (play it and you'll groan when you get the reference). The multi-player ramps up the difficulty so that the early boss you may have beaten with a few fire spells now requires all of the members to really duck and weave and fight effectively. It also adds a layer of competitiveness that KH doesn't really have.
I say that in the coming months after the release of KH 358/2 Days, if you buy it and don't have friends who also own it, don't fret- it's still a good game (a great game by DS standards, and definitely better than most $60 dollar games you find these days). But add in a friend or two to the mix and things get rather addictive.
As others have said, the one big issue here is camera turn speed and fiddling with lock on, but many games on DS have similar or even worse problems. If your one of the many who are familiar with the Monster Hunter series, then the camera system is most likely not going to give you much grief.