I like this game and I like the Kinect technology. But I am not sure if this has enough activities to keep you occupied forever despite its claims. I think that you probably will need to do what exercise addicts do and cycle through different kinect fitness disks to keep your enthusiasm up.
Ok- it was a toss up between the two fitness programs initially released. I've got into a rut and am not fit (and too podgy). The "nice and easy" program (huh!) seemed the most suited for me out of the many, many exercise classes. This is 13 minutes of repeating bouncy arm and leg movements and trying to keep up with stick figure Barbie, aka the trainer. Thankfully the program automatically pauses when you collapse part way through. I've done a few days only out of the 12 (it's quite easy to keep coming back to it) - already I feel an inch taller and I've got a slight bounce to my step, I'm sleeping way better (middle aged insomniac). Impressive.
The Tai Chi and the Boxing (disco with punches) are very pleasant, without at the moment being mind blowing - but don't seem to have many variations. I'm not overkeen on the gym games- Kinect Adventures is way better at getting you moving!
If you have no patience then you will get a little irritated with the two phase hand operated menus you have to use to navigate everywhere- it took me several days to work out how to even exit the game (out of the activity and select the Kinect hub). Also if you do collapse part way through, you have to reactivate the kinect tracking by walking towards and back to it. And you're portrayed on screen as an orange or blue blob as seen by the infra-red camera- it's a bit disheartening for the very blobby!
Compared to the Wii, you actually do get to do the activities at a reasonable pace without faffing about going through menus and scores. It also allows you to do enthusiastic arm and leg exercises simultaneously (the Wii always constrained you because you had to make sure you didn't damage the delicate electronics of the board). And no stupid controllers to pick up and put down. Superb!
UPDATE: 2 WEEKS IN- I've completed "Nice and Easy" and switched to "Break a Sweat", which has increased the workout time to 20 minutes and contains completely different exercises. (I did try out "Sculpting" but it seems to have a bug which stops it from counting down the exercise repeats). Er, inch off bust, inch off waist, half inch off hips. No change in diet (which has been fairly restrained for 2 years without any weight loss). A bit of extra bouncing around to Kinect Adventures etc. At one point I had worked up to 2 hours a day on the Wii Fit without any impact on body shape, and losing weight is a big struggle- so after TWO WEEKS on the Kinect I am well impressed!!