The movie is the best in the Index series, but that isn't saying much. Animation is improved, but it still bears all the sins of the series: Constant exposition, convoluted plot, and the same tired ecchi jokes. It also ignores the ending of Index II despite taking place right after it.
A remarkably dull sequel that progresses slowly with various non-sequitur arcs. When not in a monotonous fight scene, it's the same tired “jokes” of accidentally seeing a girl changing or naked, over and over again.