Can a show with pretty solid world setting, likeable characters, good action pace and good animation turn out to be mediocre? Index proves that indeed, it can. And this fact really makes me a sad panda. Why? Well Index got 2 really amazing ideas for character powers - ability of an alchemist and ability of certain esper called Accelarator. I won't spoil you the content, but if you watch this show you will understand the unbelievable potential of those 2 powers. And even with that the show fails to deliver. Let's check why...
1. Index - supposedly main heroine of the story is actually playing a major part in first story arc (which lasts for 6 eps). After that she either isn't there, works as comical relieve or plays some minor role. Frankly - the show is rolling without her, and desperate tries to tie her to completely unrelevant story arcs are more of a nuisance than help.
2. Lack of any serious plot line - show is basicly a few stories, rashly glued together trying to fool viewers that the storyline is moving, while any real changes were left (theoretically) for season 2 (if it comes out some day). Why is that? Well the main focus of all Arcs (except Accelerator side story) is Touma with his rule-breaking Right hand. But he is character with 0 growth. We haven't learn a single thing about the origin or true nature of his power. His harem grows larger with each passing Arc, yet there isn't a shred of change in his attitude towards the girls. He simply meet new "harem members", secure a spot in his party by doing the neccasary quest for the "target" and then moves to the next prey. The only 2 characters that actually grow during this show are Accelarator and Misaka (the real one, not the Misaka sisters).
3. Repetetive setting of Arcs - apart from Angell Fall and Accelerator side story arcs, the setting is exaclty the same, while only the players and the toys change. It goes like this:
a) Touma meets new girl
b) New girls have some sort of trouble, but don't want to get Touma involved
c) Touma gets involved and fight whoever is the cause of trouble, succeding in dealing with them but getting hurt in the procces
d) Touma is hospitalized and the girl is grateful
Once the pattern becomes visible it makes all the new fancy ideas less shiny, and the only thing left to enjoy is: "What type of power will the opponent/ally have this time"
So basicly this show even with an interesting world setting still fails to deliver. To give a hint how it could be done properly I can only send you to watch Darker than Black. It has similar build ( short story arcs, focused on main character vs esper of the week) but it actually manages to progress the story and the characters. And than it wraps it all up with average but acceptable ending, that doesn't close the possibilities of the world, but finishes up the character storyline.
Anyway - getting back to Index, the animation while it's detailed and neat isn't really original. Almost every new anime about Magicc have some glowing magic circles, shining ray of light, lightning, fire and water attacks, explosions etc. The strength of the show is indeed the core ideas for powers, but the execution (while splendid - just what you would expect from J.C.Staff ) is nothing new.
Ending the review with the usual question - To watch it, or not to watch it? If you've seen lots of stuff already, and have some free time - sure why not, this show while lacks spine still manages to bring some level of entertaiment. But there are many better shows than this, so I wouldn't put it on top of your "must see list"