As I watched the first episode of the series, I thought to myself "this could be a really great anime. It has everything there." Unfortunately, it didn't quite live up to these expectations; it was, by no means, a terrible anime however. The concept of dreams and how they are displayed in this series is rather interesting, and many things that are slowly revealed throughout the series are extremely interesting. Anyways, on to the story.
This story is well done, but it had potential to be a lot better. A few things that they mention throughout the series which are mentioned, they just kind of leave alone. If they had ran with a few of these ideas (which they may do in the off chance that there is a sequel) could have made this an excellent story. Unfortunately, they just dropped a few hints that could have helped, and leave them at that. However, even with that, the story is pretty good. They do a good job of making a world with moral ambiguity. This gives the story a good deal of depth and reality. I did not see any major plot holes, which is always a plus, but the story has some, smaller, more predictable parts in it.
Being a JCStaff series, you have fairly high expectations for all of their animation and designs. Unfortunately, it's pretty obvious that their B-team is on the case here. Index II seemed to take all their funds, and it shows. Especially in the earlier episodes, the action is... lacking and the character designs tend to be subpar. This is fixed, more or less, by the end of the series however.
This series has a GREAT soundtrack throughout, having good, up pace orchestral pieces for many battle sequences and a wide range of background pieces for the rest, often setting a great mood throughout. They do a great job using a lot of unknown voices to get the job done. Merry's voice actress has a very similar voice to a few different, more famous voice actresses, but is kind of hard to place. She does the ED, which is fairly good, and OP is strong as well.
The series has some good characters and some clichéd characters, but some of the more interesting characters never get the attention they deserve. It lacks any character that really is just amazing, and, because of this, doesn't deserve an overly high score.
This series is definitely worth watching. While it could have been great, it settles for good, unfortunately. But that isn't all that of a bad thing. It is definitely a solid series worth looking into.