I just saw it. While it's not deep or anything I had such an amazing time. The trailers made it off as if it would be as fun as nails on a chalkboard with all of the dumb humor but within the context of the film it works quite good. I never liked Ben Affleck's characterization in the past films and without the heavy handed "Do yo bleed? or "Men are brave" spiel, he can be pretty spectacular to watch and it feels like he finally found his groove here and I just his more mellowed and sort of introspective performance.
Keaton is also fantastic and his fight scenes are straight out of the Arkham games. As a child, I was never one of those who pictured that he couldn't turn his head or that he fights stiffly, or that some fans keep insisting he's 4 feet nothing. He's Batman and any Batman, regardless of actor is 6"2 and is a master of hand to hand combat and that's what we get here.
I also never liked Ezra Miller as the Flash but he's thoroughly convincing in both roles here, he is definitely far more compelling than he was in any cut of the JL movies.
Finally, there are of course cameos that were kept secret with some you'll probably won't expect so I suggest if you have any interest in the film, go watch it and have a good time before people start spoiling some of the really unexpected surprises.