So, there's now a spoiler alert here, so don't get all pissy if you read this post and learn something you didn't anticipate.
Kain is right: it's not as bad as a lot of critics are saying. It's also not a good movie. It's probably not as good as Man of Steel and it's far and away worse than Nolan's Dark Knight Trilogy. Marvel's films curb stomps this second iteration of DC's fledgling universal-spanning franchise. It's clunky while being too long; superficially intelligent; and completely mischaracterizes its main characters.
The most fun character in this, Affleck's Batman, is so grossly represented that I almost walked out of the film. Batman DOES NOT KILL. The first time you see him kill someone, it's in a dream sequence, so I was like, "Fine. A pass." But when he's murdering people with gusto later in the film during the "real stuff," and doing so with abandon, I was furious. And he does more of it throughout the film. Hell, he's ready to KILL SUPERMAN! Yes, I can buy Batman finding a way to contain him, but outright murdering him? NO!
As for Superman, his animosity towards Batman makes little sense when he should be worried about how divisive his presence is on a global level. Why he's so focused on one man in Gotham to the degree that he is comes across as even more forced than Batman's hatred. And, yet again, Superman is pretty morose in this film.
Lex Luthor... The concept for this character (indeed, the concept for the entire plot) was fantastic! He's a tech guru who believes that Superman is a threat and manipulates both Batman and Superman (both far too easily) into a fight. Oh, and he knows everyone's secret identity, apparently for years, which begs the question, why not just use that against them rather than some elaborate, if fun, manipulation. And that's kind of a problem with the film in general. There's all this extra crap floating around that just convolutes any real character study that maintains its ties to the source material. As for Luthor, he's another psychotic. That's right, yet another faux Joker. It's like folks can't accept the possibility of a super villain who's just a greedy, bitter ******* who's jealousy becomes an obsession. Nope! Nope! He has to be crazy.
So, what's good about this film? Like I wrote a paragraph earlier, the concepts the film tries to explore are great. The manner in which we see heroism or feel safe are all explored. The fear of having someone with so much power on the one hand and the feeling of security on the other. And there's plenty of eye-candy. The film is gorgeous and the fight sequences are spectacular (when Batman's not murdering people).
I think Kain does an excellent job summing one of the major flaws this movie posseses. Its lack of emotional intelligence. Aside from Batman's weird PTSD-induced visions, what motivates these various characters is so under explored it's damning. Why they do what they do makes little sense. Batman goes from hating Superman so much that he's ready to kill him to suddenly being his friend? The Senator portrayed by Holly Hunt (I think) doesn't trust Lex Luthor, but we never really understand why she's really after Superman (and we NEVER learn). Lois Lane knowing that the kryptonite murder spear Batman made is necessary to defeat Doomsday is never explained. There's a lot of these plot, story, and character holes because Snyder is less interested in story telling and more interested in imagery. No, he's not as bad as Michael Bay, but at least Bay doesn't pretend to be anything more than someone focused on spectacle.
So, in the end, this is a seriously flawed film in which the heroes aren't particularly heroic or sensible. Aside from Wonder Woman (who is just sort of... there), the heroes are either murderously angry or unsatisfyingly morose. These aren't the World's Finest; these are the Watchmen aping as the Man of Steel and the Dark Knight. And it's a shame.