As someone who works overnight shift work and really didn't manage to grasp the concept of exercise FULLY, the Wii fit got me on the right path. Even a few minutes a day can help with balance (which I'm now fully aware of at ALL times..I say as I'm correcting my slouch) and the Wii Fit Plus games are just hilarious to do. I've gotten my fiancee in on it and we do yoga together.
Since I've gotten the Wii Fit, done it regularly (read: EVERY day) and watched my eating habits, I've dropped almost 10 lbs in less than 2 months. Although that doesn't seem like a lot to most, the wonderful thing is..It will STAY off instead of a rapid loss (which can lead to rebounding and weight gain).
It's not going to make you insanely buff (for example, for the tricep extension I use my free weights since I've been working out for a while and feel using the Wii-mote is a little ridiculous) but it's a great way to get motivated, it's so much fun and it's a good start to a healthy lifestyle.