I've been a little surprised how hard it is to find information/reviews/conversation about this game. It seems like no one has reviewed it except Amazon users and YouTube rando's. So, in case someone is looking into it, I think it's worthwhile to say that I'm a fan, and it's worth buying...if you have enough room, and you don't expect miracles.
My girlfriend and I have only been using it for a week, but it's already earned its $50; which is also what I pay monthly for each of our gym memberships. However, since the workouts are limited to 30 minutes (after the initial 45 minute test session), it's been a lot easier for us to move the coffee table and couch and put in 30 minutes in the living room; rather than take 90 minutes to bundle for the cold and head to the gym.
I used to be pretty fit; but after two years of letting myself go. I've been finding it really hard to get back into a proper workout routine oriented toward weight loss, aerobic exercise and general fitness rather than weight lifting and mass gain. So, even when I went to the gym, I was doing the wrong things, and I would get bored out of my mind on any of the machines.
This game has really helped me keep my focus for aerobic exercise...once I let go of the embarrassment of running in place in front of my TV. The exercises are varied enough during each workout, and the pace quick enough that I'm sweating like crazy...and feel like I accomplished something...which says a lot.
It's a supplement to my gym time, or actually, the gym is starting to be a supplement to this; but either way, it's not a complete replacement. And you'll need to supply your own willpower. The instructors give are a little interactive, but really, you have to stick to your form and the times; it's not like they're going to punish you; but it's good to have them there to direct you.
Get the demo, try it it out. I find it worth it.