I watched it last night. I thought it was good but not a masterpiece.
There's little emotional weight to De Niro's character, in my opinion. The betrayal at the end is tough, but it's tough mostly because we see how and why Hoffa valued Sheeran. How he loved Peggy in a way the movie fails to express Sheeran does until it's too late, and by then we are supposed to sympathize with a man losing a family he barely values at all for 2.5 hours. What makes Sheeran tick? Why does he do the things he does? I'm not really sure beyond his military background ensuring his loyalty to orders, but this does not make an interesting or deep character.
Every other character, on the other hand, is really well-realized. I love love Pesci and Pacino in this. Pesci in particular steals the movie I feel, constantly managing to feel like the older loving brother but also the underlying threat to everything he does. The way he looks at Sheeran after Crazy Joe embarrasses him in the club.
I can't help but feel centering this movie around Peggy might have been a more interesting, though quite different, movie. She feels like the real beating heart of the movie, the intersection of the three main players (Pesci, DeNiro, Pacino) that still evokes emotional response in the viewer. Pacino, in DeNiro's betrayal despite Hoffa's complete faith in him, gets some of this too. But this is only a part of the movie, whereas Peggy has been getting betrayed by Sheeran as a terrible father her whole life.
Many people who don't like this movie call it boring, but I rarely thought it was. Instead when I wasn't enjoying it, I was feeling frustrated by it. Digressions like Crazy Joe didn't bore me, but I also don't feel they quite fit. It felt like a part of many moments in the film that it veers away from character drama into "did you know this happened in history?"
As far as the de-aging, it's largely okay besides when the actor's bodies let down what the CG is doing to their faces. Very distracting though were the fake blue eyes in a failed attempt to make DeNiro seem Irish instead of Italian.