I saw it at Target yesterday, but Amazon says they won't have it until the 17th, I believe.
It is the same game as the Yourself Fitness that was out a couple of years ago for the PS2.
There are some good reviews at Amazon. From what I've read it's more of an interactive workout dvd than a game, so I think some reviewers gave it a lower rating because of that.
I've been using My Fitness Coach for about a week now and I absolutely love it. It is sort of like an interactive workout DVD but every workout is different which is great for people who get bored easily (like me).