My sister has the Wii Fit. She hardly uses it and I'm so jealous because I LOVE the hula-hooping (GREAT for abs) & jogging (totally puffs me out!). But most of all, I adore the yoga programme. The fitboard monitors your balance & while the stretches burn a bit, they make me feel limber and unwound afterwards. I can't afford to buy one of my own at the moment because I'm saving for travel, so every time I visit my sister I'm always trying to jump on and have a play, much to her boredom! ;)

I LOVE the Wii! Last time I dieted, Dance, dance Revolution and Wii Fit were my main form of exercise! It worked well and it's fun! Wii Fit is also good for keeping a record of your weight progress. You can set goals and everything. Usually I would alternate days between DDR and Wii Fit.

Wii programs
 

The best cardio workouts for the Wii, in my humble opinion:

Gold's Gym Cardio Boxing... you will need to work up to the point that you have unlocked several layers. But it's a good solid cardio workout.

Walk It Off... just walking to music, but it works! Build your island habitat while walking, unlocking more and more music and other goodies.

Outdoor Adventures, using a floor pad, running, racing, log jumping, trampoline, it's a lot of fun and a real workout. I get this one out when the kids come visit, they love it.

I love Outdoor Challenge (I think that's the one that LisaAnnie was referring) and the mini games on Monkey Ball Step & Roll. (I like the games)

I bought the Wii fit plus with balance board which although I like for keeping track of my progress, I find the exercises too easy/boring. I do like the yoga part for warming up or cooling down though.

For cardio on the Wii I prefer Just Dance and Just Dance 2, I do 30 minutes of it and I'm dripping with sweat! It's fun too, even though I'm the most uncoordinated person in the world :)

I recommend renting a few games from your local video store and seeing what you like, that way you aren't wasting money on buying games you don't like!