Just saw it and loved it. I've been skimming this thread and lot of people seem to be chanting "Superman never kills" like it's some kind of mantra, but Byrne had Superman execute three Kryptonions all the way back in 1988 in Superman # 22 (Vol. 2).
Plus, Superman presumably killed the depowered Zod, Ursa, and Non in Superman II
when he threw them down in the ice pits.