The single player gameplay is very similar to the new DS version. The final boss battle is awesome though. Nice way to keep it fresh. Also it has some replay value because after you beat the game, it unlocks World 9. In order to lock levels in World 9 however, you need to go back and collect all the star coins in the first 8 worlds. So if you collect all the star coins in World 1, that unlocks level 9-1.
The multiplayer is where it's at though. Played it with some family over at Thanksgiving and it was wild. Multiplayer with 4 players equals ultimate jackage (e.g. jump on other players, throw koopa shells at them, throw others into the lava).
We eventually got tired of dying too much on the more difficult levels and it evolved into more team-based play with only the occasional guy being thrown into the lava hahah