before I tried wii fit, I didn't expect to like it. The yoga portion of it got so much publicity that it really felt like a cheap jump on the yoga bandwagon. rather, since starting wii fit last week, I find I rather enjoy it.
Since it's built around the balance board, almost everything focuses on the core muscles: not only the yoga poses, but the strength training, aerobics, and balance games too. It obviously won't give you the meditative aspects of a good yoga practice, but the feedback it does give about your yoga poses and other exercises is pretty amazing. for most activities it gives you a range for your center of balance. you get immediate visual results about what's happening with your center of balance and with practice, you figure out what you can do to correct it. I imagine for beginners it's great for making sure you're not cheating on your exercise motions, but for me it's just fantastic to finally be able to fine tune my balance and posture.
although some people would disagree. when you're between activities it gives you a green glowing representation of your center of balance. according to eiocy, the green orb barely shivers when I stand still showing that I have "ridiculous posture". apparently I have way better body control and I've inspired him to take more yoga classes.