Fun, funny, and simple... but lacking something.
I bought monkey ball for multiplayer fun. It turned out to be a huge dud and people were saying this is much better. So I traded it in for this. Really glad I did...
The multiplayer is pretty fun, but the games get repetative with the movements after awhile. We still find ourselves playing Wii Sports when my friends come over. But this game is still really fun and if you want to add some variety for your parties, this won't hurt.
The singleplayer is the same as multiplayer. You can't play the multiplayer games without beating them first by yourself in singleplayer. I had a lot of fun singleplayer. There were a few games that aren't fun at all, but only like 2-3 at the most and even then they weren't that bad/hard to beat.
The dancing games are by far the funnest to play. Wish they had more of them and a bigger variety.
The bottom line. Get this is you're looking for a multiplayer (party) game to play with friends. You'll be very dissapointed if you're looking for any type of story and single player only. I would also wait until it comes down in price, $30ish or so.