I have zumba on the Wii. It is a lot of fun, my only criticism is that if you have never done zumba before (which i haven't) it is very hard to follow at times because the dancer is more of an outline rather than being in detail so you can't see exactly what is going on always. For that reason i'm also going to get the DVD so i can learn the moves properly.
Zumba is the best fun i've ever had exercising. I have lots of exercise games for the Wii and this is the only one i've gotten out more than once and actually look forward to playing. The sessions are a nice length at 20 minutes which is just about right as i don't think i could cope with a lengthy session on this diet, and you can work up a really good sweat in that time without even feeling like you are 'exercising'. I feel it the next day as my bum, tummy and leg muscles all ache!