Well, basically everything you've read is true. It's not the Batman movie we've been waiting for since 2008's The Dark Knight. It's a mess. The script is weak, the villain is over the top obnoxious—it's completely unbelievable that he's able to manipulate either Batman or Superman— it's way too serious for a movie about grown men dressing up in costumes to fight bad guys—but it's biggest sin is that it's boring. Above everything else, what matters most is if it's entertaining, and for the majority of its run time BVS just isn't that interesting. I don't care about the characters, I don't even really care if Batman kills Superman or not (which he certainly won't, since this is just a prequel for the real movie: Justice League, I–XXV, and a great way to sell action figures and lunch boxes), but I've gotta admit, those costumes do look great. BVS easily takes the prize for best looking Batman costume to ever be filmed. For once Batman's wearing something that he looks like he can actually fight in, and on top of that it looks like something I would want to wear too when I pretend to beat the shit out of my little brother. It's just a cool costume. It's cloth, it's dark grey with the right amount of black trim. The Batmobile pretty much still looks like the Tumbler from the Christoper Nolan movies, but it has machine guns on it now, so, I guess that's cool?
Speaking of machine guns, there was a lot of extreme violence hinted at in this movie, which was another thing that I wasn't sure how I felt about. I mean, it's so boring it's hard to keep track if the movie is trying to say anything about anything (spoiler alert, it isn't), but when violence serves no purpose, when it's not saying something about the overall theme of the story, or at the very least, pushing the story forward (think T2, or any good action movie from the hay day of action movie-dom) then it just feels empty, which makes the audience feel empty, which makes them once again bored.
There's also some terrible CGI scenes of Cyborg and a few other random characters they threw in to connect it to the Justice League movie that doesn't exist yet. It's really awkward. There's also a dream sequence where The Flash visits Bruce Wayne, which also another terrible CGI scene that feels like they threw it in last minute when they remembered this is supposed to just be a movie to set up that movie.
On the plus side, Wonder Woman was pretty great. The actress does a good job, and minus one shot where you see just how short her skirt is, her costume isn't overly sexualized like Black Widow's (the only other female superhero on the big screen at the moment). Also, I didn't fall asleep, and it was still slightly better than Marvel's Ant-Man and Thor 2. But that really isn't saying much.