1) You need a DS to get all the features, and use pokemon from your DS game, otherwise you are stuck with rental pokemon from in-game that are bad and hard to win with. You also get a surfing pikachu as a prize for beating the game, without a DS that is useless.Originally Posted by d3moliti0n
2) Online works pretty well, it's a little slow but I didn't have problems with it. It's just turn-based batteling. Finding other players to play is pretty simple, and you can add your friend's friend codes to play them any time you both are ready.
3) Gameplay is a straight-forward colloseum battles. Only battles. The single-player is battling through tournaments to unlock costumes and prizes. Not very detailed. I'd say try to find a used or bargain bin copy, it's not really worth $50 to most people. I got it on release day with the Harry Potter game, and still play both ocassionally.