Hi Steiny & Sharon,
I use my Wii every day. I have to say though, I don't use the WiiFit much anymore as I have got a better program that gives you a better workout (it's the Wii Active 2), but when I did use the WiiFit, I set up the Freestep, for 30 minutes and then you could switch to normal TV or put a dvd on and the remote acts as a counter while you do it. The time passed really quickly. I bought a step extension so the step was higher, thereby giving you a bit more of a workout.
I have found that you should wear shoes while doing it, a good pair that aren't "clunky" to give you comfort and cushioning. I have had a knee reconstruction in the past, so my knee is quite vulnerable. It did ache before when I didn't wear shoes, less so now. Now I don't know if that is because I have been working it and it is getting stronger, or because I am wearing shoes, though!