I was planning to wait and buy Rhythm Heaven Wii when it arrives on North American shores sometime later this year, but after reading these impressions and seeing these videos of the just-released Japanese iteration of the game I'm seriously considering changing those plans and buying the Japanese version now and the North American one this fall.
Another reason I'm considering altering those plans: You just know the folks at Nintendo of America will screw up the vocal tracks when they go to localize them--just as they did when they localized the tunes that appeared in the North American version of the DS-based Rhythm Heaven title. (Don't believe me? Watch this video and then this video. Yikes!)
(Photo above courtesy of true-gaming.net)