Great workout game... unless you have a short living room
That being said, I have a narrow living room (12' in width and only 6' between the couch and the wii sensor), several upper body workouts would not register properly when a repitition was made and the user has to "modify" the reps to allow the system to count them. Unless you have two sets of sensors you cannot have two people get credit if they workout at the same time.
The online portion of the game is great addition / improvement from the earlier fitness games, however the system frequently searches for network data which adds to the downtime that could otherwise be spent exercising,
Overall worth the money, but it is not perfect.