BvS features an aged, bitter, violent and darker incarnation of Batman who's obsessed with stopping Superman, fearing that Superman could be a potential threat to mankind in future if left unchecked. On the other hand, Superman also questions Batman's acts of vigilantism that are becoming more brutal and violent. Both heroes were unaware by the fact that they're being manipulated by someone who's intentionally escalates the conflict between the two for his own nefarious reasons. The story strives to explore human and philosophical elements, and it succeeds on many levels. This isn't the older days, where Superman is simply accepted as a saviour with good intentions. Today, we live in a cynical world where people are suspicious of each other and people are motivated mainly by their own selfish concerns. It explores the possible political and societal implications by showing how the world would react to the arrival of a god-like being like Superman. It seeks to reveal the flawed nature of these iconic superheroes by showing the humanity of Superman and the darker side of Batman who's blinded by rage and fear and gradually loses faith in humanity over the years.
After the controversial conclusion of Man of Steel, the film starts off with Bruce Wayne's flashback dream of his tragic origins (again) before taking us back to the reckless battle between Superman and Zod and let us witness it through the eyes of Bruce Wayne. He's heading to a crumbling Metropolis with falling and burning skyscrapers in an attempt to rescue as many innocent citizens as possible. Bruce looks up in the sky, witness the disaster with a moment of helplessness and realizes that despite all the resources he has in his possession, he's still powerless to change anything. The story builds up slowly to the eventual fight between the two and the climactic battle which involves Wonder Woman in the last act.
Affleck succeeds in portraying both Bruce Wayne and the Dark Knight, instantly making the character his own. He made his intentions clear in the beginning and the reason why he needs to take down Superman. He may be the best on-screen Batman of our time as his detective skills were properly shown here this time around and his fighting methods were close to source material. While Affleck's Batman steals the show, it is Cavill's Superman who's very much the heart of this story. Cavill was given more lines as Superman this time around and he tries to imbue Superman with humanity, who struggles with the weight of his responsibility to the world, showing us a conflicted character who tries to do good, to do the right thing for the world, but constantly under heavy scrutiny and criticism from every action he takes. The scenes where Superman was deeply saddened after what happened at the Congressional meeting and the confrontation between Lex and Superman (I won't spoil what actually happened) showed the human side of him as a person and not the untouchable god-like being many people think he is.
Gal Gadot is fine as Wonder Woman, who also immediately steals the show with cheers and clapping hands from the audience the moment she appears in action for the first time, with her indestructible bracelets, Aegis shield of Athena and Lasso of Truth. I'm definitely looking forward to see what Gadot can do as the character in Wonder Woman's first solo film. On the other hand, Amy Adams brings her usual warmth, humanity, and vulnerability as Lois Lane and serves as an important anchor for Superman. The most controversial performance in the film would be Jesse Eisenberg's performance as Lex Luthor. Audience and fans might love or hate with his slightly different take of the character. Eisenberg's Luthor is basically a wealthy, geeky, genius version of Joker. He's greedy, driven by ego and has a thirst for power. He envies and hates those with a higher power (Superman) than him. His worldview and motives are twisted, which makes him all the more unpredictable. In my opinion, Lex Luthor's maniacal manipulations and schemes were as great as the Joker's in The Dark Knight. There's a well executed scene - the climactic conversation between Lex and Superman that shows Luthor's true character and intentions.
There are some light humour in this film compared to Man of Steel, despite the dark and gloomy atmosphere (albeit not so much compared to Marvel films of course). A few notable ones would be the brief banter between Batman and Superman when Wonder Woman appears on the screen for the first time, when Martha Kent managed a friendly line when she meets Batman for the first time or the constant bickering between Affleck's Bruce and Jeremy Iron's Alfred. Speaking of Iron's Alfred, his progressed friendship with Bruce was very well portrayed and the conversations between them (Bruce and Alfred) provide the necessary relief for such a tense and serious movie.
However, the film's greatest weakness is its poor editing. It is sloppy and messy at times. It feels that the story is not structured properly and flowing naturally from one scene to another as it should be. You would feel the sudden pull out of one scene just as you're getting attached to it and abruptly placed into another scene that has no connection with the previous scene that you've watched. Aside from this, the film included quite a few of DC movieverse world-building scenes, with one of them feels out of place and unnecessary. It's fine for the filmmakers to include glimpses of Aquaman, Flash and Cyborg and the introduction of Wonder Woman in the film as all of them were handled quite efficiently. It doesn't disrupt the overall movie, except the 'Knightmare' sequence where Batman is wearing a desert coat. Although it provided hints at what possibly going to happen in a distant alternate future (the Omega symbol and the presence of parademons hinted the inclusion of Darkseid in future films), it feels slightly out of place as it was never mentioned again later on in the film.
As mentioned earlier, this is a definite step up from Man of Steel. Despite all the negative criticisms and mixed reactions from the public, in my opinion, the film hits more than misses and it has accomplished far more than it needs to launch the start of DC's own cinematic universe.
Note: There are no mid-credit or post-credit scenes.
My personal opinion: People should never compare Christopher Reeve's Superman with Henry Cavill's as they're adapted from different age of comic books (Reeve is from Silver Age while Henry is from Modern Age, they're different versions of Superman in different times).
I've prepared a Q&A article for BvS that many people are asking about, please feel free to read it after you watched the film: