Well, as with Wii Sports, I can only do things well with the Wii Fit that I can also do in real life. In Wii Sports, I can bowl, which I can do in real life, and I cannot play tennis, which I cannot do in real life.
With the Wii Fit, there are activities in the areas of strength training, yoga, aerobics, and balance games. Well, I cannot walk a tightrope in real life, nor ski a slalom, nor ski jump, nor head a soccer ball, and I did not do so well in these balance games.
I was better in the aerobics area. I could not twirl the hula hoop, something I have never mastered in real life, but the step aerobic sessions were a good workout and I could follow those. On the island run, I became winded after a time, as I would have in real life.
I have not tried the strength or yoga areas yet-- 40 minutes was enough time for one night! It really is a remarkable combination of hardware and software. It is engaging and takes practice to master, but you do get a good workout. You get your BMI calculated and are presented with your Wii-Fit age (which I will not share here, thank you very much!)
Time for the morning workout now. If you have a chance to try the Wii Fit, go for it!