I've played it two days so far and while that isn't enough to be a qualified expert I can say that my wife and I have had a lot of fun with the game for $10 even at the 2 day mark.
The first thing about the game is it takes a bit to get used to, but once you start to dance to the rhythm and to the moves its really fun. The first day we played for 30 minutes and traded sides with the Wiimotes to keep our arms from getting too tired on one side (I played about 20 minutes before that getting used to it). The second day we played 45 minutes and used hand weights in the hands without Wiimotes. I can say with out doubt that on medium and higher you get a workout with this game.
I would say two player is the most fun but playing with people watching is pretty fun as well. The music is great and the sound quality is very good. So far I have been just mildly sore from playing, but we have stuck to the lower difficulty for the most part. We tried hard and were both breathing hard after one song.
