When the missus said she wanted this I was, to be honest, doubtful it would be worth the money. I've played on Wii fit and thought it wasn't really a worthwhile fitness product so didn't rate 'at home console fitness'. Well after a couple of 40 min workouts (don't worry, you don't have to jump into one this long) I can honestly say its a very good workout!
I would consider myself reasonably fit anyway as I already work out 3-4 times a week but this still tired me out haha!
The menu's are fairly confusing though (could just be me), but this can be overlooked seeing as it works at what its supposed to do.