I really don't think having Superman kill Zod was for shock-value. It seemed logical to me within the parameters Superman had, and I really feel like people have made too big a deal about it.
On the civilian casualties issue, Zod had set up a plan to kill all humans, so Superman had to work as fast as he could to stop that.
I do think they went a bit overboard in having the fights right by bystanders, but since it seemed the invaders wanted to attack everyone, I don't think there was much Superman could have done about it.
