hey Polishrose, to be honest it really depends on what you are looking for.
My boyfriend got one a year ago and I must say its great fun. Its a games console which has updated the favourites, mario, sonic etc to the 21st century! I also use Wii Fit which I personally find good, when Im in the mood to do some exercise. When you want to go and do something but the weather is crap outside or you couldnt be bothered getting dressed for the outside world, the Wii Fit is a great substitute.