A real-life game of poker is much more fun and satisfying than this game.
The multiplayer's OK, if you happen to know another person with a DS who likes poker as much as you do, and you both happen to have a DS with you, and neither of you has a deck of cards, and one of you happens to have the game. Other than that, poker is a lot more fun with a deck of cards, where you can actually look at your opponent, not some cheap figure who repeats the exact same phrases over and over and over and over (I actually played this game a lot).
The single player is nothing more than mediocre. It features a wide variety of poker games (I think twelve in all), and it also has some moderately fun mini-games. You can buy stuff with your winnings as well, such as skills or items to characterize your person. And the casinos are pretty creative and kind of fun to look at. That's pretty much where the good parts stop.
The games themselves are good, but they just don't give you the satisfaction of a real-life poker game. The computer players stick with the exact same phrases, which they use completely regardless of what their hand is like. This sucks because it eliminates the possibilty of unique "tells", which is a very large part of poker. Also, the games can get very monotonous, ESPECIALLY in tournaments, where you play several hands of the exact same game over and over. The fact that all you do is play cards the whole time can also be boring (that, however, should not be viewed as the game's fault, because the game is a poker game, after all). The character animations get annoying, but if you turn them off, the game becomes even more monotonous, and it becomes almost purely statistical.
In short, this game can be useful in improving your knowledge of poker games and the chances of certain hands occuring, but its numerous shortcomings, coupled with its "unreal" factor, make me want to stick with the good old deck of cards and a stack of chips.