Bleach: The DiamondDust Rebellion takes place in the Bleach universe, as the title may suggest. It focuses mainly on 10th squad captain Hitsugaya Toshiro, so if you're a fan of him, you'll enjoy this movie, and if you're not, you might not find it interesting. If you're neither of the former, like me, you'll probably enjoy it too.
The story isn't the most original story you'll see, as it follows the theme of revenge based off of a grudge from the past. Said revenge will be executed by obliterating everything. So there's nothing special in that department. Toshiro gets involved in this act of revenge because he has a connection to the man who holds the grudge against Seireitei. One day, the King's Seal, a mysterious and powerful artifact, gets stolen from right under the noses of the squad protecting it (the 10th squad), and Toshiro ends up missing. Now, events that may change Seireitei begin to unfold. And that's where the movie starts off.
It gradually explores Toshiro's past with the man who wants to take revenge on Seireitei with sporadic flashbacks, that doesn't make a lot of sense at first, but they become more and more clear as the events in the movie unfold, and you soon get to learn the reason behind this man's grudge against Soul Society. While this way of telling the story is not something unseen, it works very well with this movie, and does give it some extra tension and entertainment value.
Long-time Bleach fans will probably enjoy this movie because we get to see many characters we've not seen fight for a long time fight. Among others, there's Zaraki at his craziest, Yoruichi and Soi Fon with their Shunko, and Ikkaku with his bankai. Of course, there's a lot of icy fighting courtesy of Toushiro.
Another thing I believe long-time Bleach fans will find enjoyable is the animation quality, which is at the very least astounding. With awesome lighting effects, very fluid character movements and high attention to detail, it surpasses the normal quality of Bleach's animation by many levels. If I could, I'd set the score to 15/10.
The soundtrack is awesome as well, with astounding tunes that fit right into the mood of the movie, amplifying the scenes and events as well as a soundtrack should. DDR's soundtrack is one of the few that gets the honor of being downloaded to my computer.
All in all, if you're a Bleach fan, don't hate Toshiro, and if you don't mind a classic revenge-based story, chances are you'll enjoy this movie.