I read some spoilers which raise some interesting questions. Particularly when the old universes' Superman meets Batman and they discover most of his history stayed the same.
Batman: On your world Dick Grayson lost his parents?
Older Superman: Most of the Robins did.
Batman: You knew I had a son with Talia and that he'd be trained as an assassin.
Older Superman: ...Yes.
Batman: You knew that Joker would murder Jason and he'd come back to life on a quest for revenge...and you decided to do nothing.
Older Superman: ....I'm starting to understand why my Booster Gold decided to stop living in my time once he became a Time Master.
Booster Gold: Ha! Not so sanctimonious now, huh Superman?!