Worth every penny I paid for the seven DVDs (but I am not, repeat not, buying the Noir otaku soap). There are a lot of things I could say about it, but I think it’s sufficient to say that the ending is driven entirely by the way the characters were developed during the course of the series. Nothing has to be explained in terms of “the director added it to make the plot work out” or “they needed a cool fight scene here, so X did Y”.
The plot does work out, and you definitely get the cool fight scenes, but it’s because the heroines and villains are doing what they should do, given the sort of people they are and the situations they’re in.