Christopher Bird’s review published on Letterboxd :
ROUNDERS hasn't aged well, in part because when it was made, Texas hold'em poker was still more or less a niche sector of the game and most people played various versions of draw or stud poker instead - which the movie points out. Nowadays, though, Texas hold'em is practically synonymous with poker, so all of Matt Damon's narration about it comes across as annoying. Most of the rest of his narration is passable at best.
Still, I would take the narration every day if someone could rationally explain to me why, on God's green earth, Matt Damon remains friends with Ed Norton's Worm after he finds out Worm has put him literally seven thousand dollars in debt without telling him. This, after Worm has made it abundantly clear, time and again, that he will screw him over every chance he gets, and not even for money, but just because his former best friend is a full-blown sociopath. It breaks the film's credulity entirely and it never really recovers.
Still, Matt Damon is compelling regardless. So is Norton (he's playing awful, but he's doing it perfectly and the story not making fault isn't his problem; he also gives Worm just enough charm that you can almost sort of see why it works, which is nearly impossible). Martin Landau is great in his few scenes, because of course he is. John Turturro is fantastic. Famke Janssen is fine. John Malkovich's Russian accent is so bad it goes all the way around to being good, and poor Gretchen Mol gets the thankless gig of being portrayed as the shouty harridan who Just Doesn't Understand why it's cool that Matt Damon lost thirty grand playing poker that one time, which is the other reason the movie doesn't really work.