You'd better book a week or so off of school/ work because this game is heroin like in its addictiveness.
I honestly had to give this game to my girlfriend to hold onto because I was playing it so much that it was interfeiring with my work- I couldn't stop playing. The battles are that good.
The downsides to this game are that, like most Japanese games, the story and dialogue are pretty bad. The story is mildly interesting but is overshadowed by the totally excessive amount of text. Even the most patient soul will find himself skipping over the dialogue boxes later in the game after reading hundreds of cheesy dialogue boxes over and over. Another repetitive quality are the battle animations. They look cool at first but their novelty WILL wear off. You'll probably want to turn them off later in them game when repeating maps for the n'th time.
Speaking of which, another potential downside is the difficulty. I am admittedly pretty good at Turn Based Strategy as it is one of my favorite genres. I cruised through the first half of the game but hit a few brick walls with some battles which are drawn out, punishing slogs with the slimmest chance to succed under only perfect circumstances. I was hoping that this game would be challenging, but this is a bit too much. Others might find this a plus, but not passing a map no my sixth try proved to be quite monatonous.
Even though I have listed some definite downsides, I'm going to give this a 9/10. This game might deserve a 7/10 in diferent circumstances, but its satisfying sense of accomplishment after battles and serious addictiveness substantially raise it a couple of notches over other titles. Big time replayability on this one too! 9/10.