I agree with Ian, Nintendo has taken Mario too far. In the past year we've had at least eight games starring Mario, and over the next 12 months we will see Mario Party 6, 2 Yoshi games, one Princess Peach game, Super Mario DS, Mario Party Advance, Mario Kart DS, and Mario Baseball: eight more, and I'm willing to bet Nintendo will announce a couple of others at E3.
To me this is some serious Mario overload. It makes each new game feel a little less special. Nintendo needs sports games, but I'm not convinced that more Mario sports are going to sell GameCubes. This will probably be a good game, and I'm sure Mario/Baseball fans will love it, but I'm not very interested.