The acting is fantastic - not out of the park, but believable and worth seeing, Damon, Norton, Landau, Turturro, and Malkovich especially (and the showdown between the two Ripleys, pardon the reference, is nicely carried out but I felt that Malkovich's Oreo obsession at the beginning was obviously a manner of telling, but oh well). However, Norton disappeared and the ending was a little too light.
What really sinks this film for me, besides the fact that John Dahl has never risen above competent in his shooting style, is Edward Norton's self-impressed and obnoxious performance as Worm. We are supposed to find Worm to be a lovable rogue, but Norton manages to turn him into an obnoxious douchebag from beginning to end. Damon's character's repeated willingness to believe Norton is a weak dramatic contrivance.
Another movie about gambling that's largely the same as every other gambling movie. You gamble, you lose. You owe money so you gamble some more... Having said that it's a good movie and is perhaps a bit lighter than other movies in the genre.
The Gambler is repetitive because it is an accurate (and therefore engaging) portrayal of addiction. Rounders is repetitive because it runs out of ideas before it is half way through. Quit while you're ahead.