If you're an avid exerciser/fitness nut, Wii Fit will probably not provide anything new for you other than a little fun. However, if you're a busy mom with not a whole lot of time to do anything but your work & running, it definitely helps you get a little bit more working out into your day. My legs are getting strong from running but the rest of me needs a little help.
I am a little intimidated going to an aerobics class because I am fairly uncoordinated. I can do the Wii Fit step aerobics here in my family room without injuring anybody or embarassing myself. I can take a run through the virtual park with my daughter regardless of the weather. I can learn Yoga exercises without all the eastern religion stuff that usually goes with a class. Slaloming down a ski hill is possible even in June, and I can float down a river in the middle of December. I don't have to leave the house and get a sitter. I can do this any time of day or night.
I haven't gotten to any seriously high-intensity cardio exercise yet, but new activities open up the more you use the program. I have broken a sweat, however, and the yoga really works your muscles. (just ask my thighs). It's a lot of fun and combined with the Wii Sports it's fantastic for families. My 6-year-old daughter can play against my 20-something sons and still have a shot at beating them. Everyone has a great time.
I guess what I'm saying is, if your idea of a good time is 6 hours on the eliptical machine followed by 400 push-ups....don't expect the Wii Fit to intensify your workout. If you just want to supplement your current exercise schedule, give it a try. If you're a complete couch potato or are a fitness newbie, definitely use this as something to get yourself into gear. I give it 4.5 stars out of 5.