While we've still got a few weeks before the Batman vs Superman Ultimate Edition (R rated) comes out on Blu-Ray, which ends up being about 30 minutes longer than the theatrical version, the following is a non-spoilery review that compares the two versions:
http://screenrant.com/batman-v-superman-ultimate-edition-reviews-bluray/
Sounds like it does do some justice in filling in some of the major plot holes for the theatrical trailer and does sound like it is the more complete, better version of the film. However, it doesn't sound like it will be head-turning for anywhere where it won't make you like the film if you hated it. It doesn't change anything as for direction, look or tone of the film, which is a lot of what many people hated about the film. If you don't care for spoilers, they also posted an article that shows every single difference between the two versions of the films. I haven't read this one.
http://screenrant.com/batman-v-superman-ultimate-edition-changes-differences/
http://screenrant.com/batman-v-superman-ultimate-edition-reviews-bluray/
Sounds like it does do some justice in filling in some of the major plot holes for the theatrical trailer and does sound like it is the more complete, better version of the film. However, it doesn't sound like it will be head-turning for anywhere where it won't make you like the film if you hated it. It doesn't change anything as for direction, look or tone of the film, which is a lot of what many people hated about the film. If you don't care for spoilers, they also posted an article that shows every single difference between the two versions of the films. I haven't read this one.
http://screenrant.com/batman-v-superman-ultimate-edition-changes-differences/