Sad that an article explaining why to watch any movie in one sitting is necessary - especially semi-biographies where you can expect a long arc of character development. Set aside a 3+hour block of your day, or don't.
The whole movie was very melancholy, and that can easily translate into boring if you aren't either interested in organize crime figures or already fans of DeNiro, Pacino, or Pesci - doubly so for a film of this length. You probably would not feel as motivated to sit the three hours if these actors weren't driving the movie, because for the most part it felt like an extended last 'hurrah' for these film legends to work together in a classic mob tale.
However, the story itself was solid and the actors all struck their parts perfectly. DeNiro and Pesci did excellently portraying aging mobsters in a way that is not nearly as glamorous or over-the-top as in previous installments. Romano surprised me with his great portrayal of Pesci's lawyer cousin who helps out the Irishman (his acting chops finally overpowered his Kermit-voice), and Pacino did just as you would expect playing a bombastic character like Hoffa. Props to Jim Norton for doing a great rendition of a young Don Rickles panning the mob on their own turf and getting away with it!
There were parts where the dialogue felt like it was running nowhere, and some of these felt like nods to Goodfellas and Casino-style humor that just didn't land and felt unnecessary (think the fish on the car seat conversation). Also it didn't succeed in landing as strong of an emotional impact as may have been intended, especially near the end of the movie as the Irishman contends with the suffering he caused to his victims and family. You almost felt as if you were expected to feel more sympathy for the devil, but with the exception of seeing him and his old buddy suffering in the penitentiary and the nursing home, there just wasn't much emotional gravity to the things he suffered through - especially .
All in all, a slightly scattered but sobering and mildly depressing crime story with an A-list cast that saves the film.
B+