this series is awesome imo. the progression is very natural i think. conflicts of conscience have been well depicted, the differences between bats and superman have been well portrayed. even wonder woman has been shown to be true to the root of her nature. the question of whether he was right or wrong is too simple i think. i've not finished the series yet but his initial reaction was wrong legally of course. morally? if you allow a known killer to live, then he goes out and kills a family, were you responsible in a way for allowing it to happen? is the joker different from some, a rabid dog? is there such a thing as the greater good? if you believe so, you'll applaud his action with joker. there is also the question of what superman is intended to represent. even if you think his action was morally correct, his actions were disappointing in that they lessened him, set him APART from the world around him, ABOVE it.
had he stopped at declaring a ceasefire, after having ONLY killed joker, would THAT be better? with his power IS he morally responsible to stop what he CAN stop? dissertations have been written on these topics.
one thing i know for sure--this series and the questions it raises it is remarkable imo. different, challenging and refreshing. best book currently on the market imo. at least for the first 15 issues so far.....