This is a great thread. I love the Wii Fit, it's my main form of exercise when it's too hot to get out of the house with the kids.
Since the Wii isn't region free, I can't use most North American software. We have Family Trainer which just isn't as good as Fitness Trainer I don't think. I have been pretty disappointed in the offerings. But from the recommendations on this thread I looked up the new ones. Gold's Gym won't be offered in Japan but EA Sports Active will! I just preordered mine.

Woohoo!