"Muscle tone" and "core strength" were abstract concepts before Wii Fit. Now I develop them and feel myself using these new-found balance and core muscles all day long.
Even on tired days when I tell myself I'm just going to screw around on the Wii Fit and clock an easy 30 minutes, I still feel recharged and pain-free the next day. You start having fun and you end up improving yourself before it's done, like Fat Albert, hey hey hey.
Now I know how much constant pain I felt all the time, because that unnoticed pain is now absent. To quote my best friend, the absence of pain is orgasmic.