My Wii is probably really annoyed with me because I stopped using it when the weather got nicer
It really depends on what you are used to and what you are hoping for. Fit is a lot better than sitting and staring at a screen, it does get you moving and it's fun. I imagine it's a fun family game too. I don't think it's a great workout if you are looking for more intensity and the yoga doesn't impress me. However using the yoga and strength to get going in the mornings was a nice start to the day in the winter.
For a little more sweat I really love EA Active workouts and more workouts. I've also heard that the Gold's Gym is a serious workout if you like kickboxing. I haven't seen great reviews of any yoga games sadly.