I've been playing the game tonight, and find it acceptable. It has some control problems, though:
-fielding is difficult; your players will execute special moves and dives seemingly at random, or the distance from them to the ball's landing space is the cause for certain moves to be executed, and the space difference between such categorizations is negligible
-the batting system is strange; you use a meter to judge your power in practice mode, yet this meter is not present during the game--futhermore, the game uses a bizarre swing charging system that not only leaves me unsure as to when to best start charging but also can't be charged up once the ball is in the air
-pitching is not very deep at all--you can throw slow, medium, fast, or star, the last of which seems to only work well for the team captains, as most ordinary players have star pitches that really don't do anything but make stars fly about and the ball go slow...the game also uses the "RBI Baseball" viewpoint, as opposed to the "Bases Loaded" viewpoit of behind the pitcher (as is commonly seen on TV), which means no high or low pitches, just left and right
-the star point system biases strongly toward those characters with good pitching skills, as team captains use less stars than their teammates
-daisy and peach don't look as good as they did in golf and tennis--they're wearing approximately the same outfit (peach is now in shorts, though) but the art isn't as strong as before--forgot to see if daisy still has her potbelly
-baserunning is counterintuitive (at least to me), as you push the direction on the D-pad of the base you want the runner to go TO, instead of the base he is on
-I swear to Jehovah I push "up" on the control pad (second base) and the fielder throws to third. Several times. The standard GC controller is too chunky for this game, but luckily I have a Hori SNES style pad for this game
I think that's about it. Other than all this, it's charming and a decent way to kill a few hours.