Got this off my friend yesterday for $15. To sum it up, it's like SSBM: The Puzzle Game. XD
Really, there's just alot of stuff you can do in this, which is pretty amazing for this kind of style. Each of the many planets you can play on have their own special 'gravity' and effects, like some that might launch quickly, but only a few Meteos can escape at a time, or ones where you have to incinerate Meteos (but they won't launch!) then fire more Meteos near it to make actually fly off the screen.
I wasn't planning to get anymore games before the Wii launch (and especially not a puzzle one), but I'd say this one is definetly worth it. ;D
EDIT:
Oh yeah. Some other things that make this great are all the little added-in "quirks." Like how on the main menu screen, you can actually move the buttons around (doesn't do much, but it's cool Xp ).
The music is also rather interesting. During gameplay, a rather repitive soundtrack will play. However, you actions actually add to the music. Make a line of meteos, launch them, use items, hit your opponent, whatever, all of it adds to the music for a crazy, 'tripped-out' experience in the music alone. =D