Much better than previous Index installments, not nearly as much eye-rolling ecchi, but a lot of the same sins. Villains are all good guys by the next arc, (and there are a lot of arcs) and the overarching plot is needlessly complex, and solved via deus-ex machina anyway.
A Certain Magical Index: The Movie – The Miracle of Endymion
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 Certain Magical Index II
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.
A Certain Magical Index
Every anime sin is committed here in a show that feels like it was Frankensteined together out of everything kids in the early 2000s said they liked about anime.