Just finished this movie and it was pretty bad outside of Michael Keaton. His scenes make the entire film worth watching. And it's not just because I like Michael Keaton. The filmmakers actual did an amazing job with his action sequences too. It felt like watching the best parts of the old Tim Burton Batman combined with the best parts of modern special effects. After seeing this, I'd really love to see a movie that tells the story of old man Bruce based on Frank Miller's the dark knight returns comic. And Michael Keaton is the perfect age to star in it.
As others have said, the CGI is terrible. Like the worst I've seen in 20 years. And I disagree with dragonlord about Ezra miller's performance. I think he was bad.
First of all, the writers screwed up by trying to make the flash into Peter Parker. But if you are going to do that, then Ezra Miller is the wrong guy to play that part. He doesn't ruin the movie but he's definitely not one of the strengths.
I loved all the clever cameos although most of them come in the form of awful CGI which devalues them quite a bit.
I agree with others that this might be the best DC snyderverse movie, but only because the others were so terrible. Without the Keaton batman scenes this movie wouldn't be worth your time. But since they're there, it totally is.