TL;DR: This is the first "fitness game" I actually feel can help you get fit; and I think it will do a good job of it at that. It isn't perfect, but actually adds (a lot) to the experience.
:: Update/initial impressions ::
For those who don't know, the main attraction here is the 2 arm/1 leg sensor system that comes with the game. One of the arm sensors also doubles as a heart rate monitor. This allows the game to tell if you're doing your exercise or not.
I started the 3 week "Cardio Kickstart" program on Monday at the medium difficulty setting. This program is pretty much what it sounds like - a mix of cardio and toning type exercises. Right now that's what I'm wanting, but will likely turn the focus more to gettin' swoll' once I get some cario done for a little while. I work out Monday, Tuesday, Thursday, and Friday. I've heard that hard difficulty is no p90x, but that it's more than enough to kick one's butt into shape. You can also change the difficulty at any point if you're feeling particularly frisky (or lazy) that day. I haven't studied the programs in-depth, but from what I hear the 9-week is set up in three phases to keep you from plateauing, and is well-balanced.
Day 1 and 2 both went well. Medium workouts last 20-25 minutes. There is something very fun about doing an exercise and being prompted to do the action on screen. For squats, I can see my avatar standing there, he squats when I do (along with an indicator on the right showing my goal for how far down I squat), he comes back up when I do, and I get credit. They throw in fun environments and games, like "pedaling" your way around a bike track - high knees to pedal, low squats to gain speed downhill, and squat jump to do a trick on a ramp. It really does help with the motivation.
The heartrate monitor (while not state of the art, it works well) gives you good on-screen feedback as to whether or not you're dogging it. All the stuff you do is automatically tracked for you - completed workouts are shown on the calendar, your calories burned can be seen, etc. You can also check your stuff online at their website.
Workout groups can be joined online to keep each other encouraged. I haven't joined one yet, so I can't comment 100% on exactly what is included with this.
There are a lot of options available. You can configure your profile to show weights while you work out instead of the resistance band, and it adjusts accordingly. You can create and save custom workouts. You can import custom playlists to play while you workout. You can go to your diary and keep track of other activity and what you've been eating, and are given some responses based on that. It sounds silly, but it really does help you be mindful of how you're living.
So things are good right now; the real test will be to see how things are going 3 months from now. It's not perfect - there were a few exercises where the detection didn't work well for me at first because I wasn't 100% sure what it was looking for. For example, I spread my legs too far doing squat thrusts, and so when I came back up it hadn't detected I was the whole way up yet. That was pretty quickly rectified. It was annoying to be automatically shown a tutorial before proceeding to an exercise, even if it was the second time I had done it. I'm assuming there is an option to turn this off, because it was annoying to dig for a controller to skip it in the middle of a workout, especially considering there is a "press triangle to view tutorial" option WHILE doing the exercise.
Here's my bottom line on any exercise program: different things motivate different people. I liked p90x due to the fast results, which in turn kept me motivated. It just won't fit with my schedule this year, though. Having on-screen prompting and cheering also keeps me motivated. So "is this program worth it"? That's like asking, "why do people pay to run at a gym when they can run outside?". My personal feeling is that if something works, and you value your health more than $40, then yes it is worth it, especially when you consider the amount of green being healthy saves over time. Your health is worth far, far more.
Strengths of this program:
1) Variable levels make it easy for anyone to get into and adjust as need be
2) Custom workouts allow you to do this even further. I'm seriously considering putting together a p90-esque free weight custom workout.
3) Trophies for working out. It's cheesy, but it actually motivates me.
4) Tracking you makes sure you actually work out. It's the perfect accountability partner.
5) Get more sensors, and you have some co-op action.
6) It's fun!!!
It's not perfect, but I think the pros outweigh the cons by far. I highly recommend this for the money.
I believe it needs Move, or at least to get the most out of it, though.