As a big fan of 2D platformers, I'm really glad this got released. I guess there's not much to say, it's your average Mario platformer, not many innovations, but hey, at least the difficulty level is at least decent (compared to the DS, at least), and the world 9 levels are quite fun.
But nevertheless, I beat it in a weekend, still, fun game, and a definite must-have for any Wii owner who at least liked the older Mario games.
I especially like the multiplayer, and it's actually not as easy as you'd expect (except for the A-button, which makes everything just broken when it comes to not jumping to your doom), and 4-player coin battles and the likes can be quite fun.