[warning, the following is by an avid ps2 pop'n player who hasn't played the wii version]
Gone with the old classic pop'n skin and in with the new abomination. Pop-kuns surely get lost in this mess of a "stage". Miis dancing in the background *shudders*. Further making this purely into a party game is the fact that there is no scoring. Just three trophies: one for passing, one for 100% bar and one for full combo. And why is it that pop'n wii must have the same wii-like menus every other game has?
At least Beat'n Groovy looked like Pop'n Music...