I own and love all 3 Just Dance games (along with the Smurfs and Michael Jackson). The variety is great, it's exercise, and it's mostly good clean fun. I'm very hesitant about a few things that are on the game though. For examples:
Boom: Full of thrusting hips and shaking your rear - not suitable for a young adult in a club, much less a small child!
Promiscuous: Lyrics include: "You expect me to just let you hit it but will you still respect me if you get it. I can see you with nothing on feeling on me before you bring that on"
In between there are a few drinking references (I don't understand why Kesha can say she has beer, but they edit drunk out), I do play the game a lot with my kids, but they know they're not allowed to play a few of the songs within the game.