7. The Effect On Batman
Perhaps out of all the heroes, Identity Crisis has the most significant effect on Batman. While many would have expected him to be front and centre of the story using his detective skills to catch the killer, it is in his role as mentor and friend that the most significant impact happens.
Then Robin Tim Drake is caught between two fathers - his biological father Jack Drake and his mentor Bruce Wayne. As the story progresses Robin must choose between the two, which ultimately ends in Jack Drake's death and a schism forming in his relationship with Bruce. It places Batman in a position of yet again failing one of his charges.
The second aspect ties into the events of Tower of Babel, where Batman shows that he does not entirely trust the League and that he is prepared should they go "rogue". Identity Crisis shows his fears are not wholly without merit and that his so-called "friends" had wiped his mind of their actions.
These events lead directly into the construction of Brother-Eye in Infinite Crisis.