I purchased the Wii Fit Plus for my wife this past Christmas. Our gym had gone out of business, and this seemed pretty interesting for us (late 30s). We had already owned the Wii console from the year before, but we had lost some interest as had our kids (4/6). Well its easy to say this changed everything!
The addition of the balance board completes the whole 'virtual reality' experience of the Wii. I am amazed how the board can detect your arms flapping or hips gyrating to really immerse you into the game. The balance and training plus games (new to wii fit plus) are tons of fun, and we have spent dozens of hours playing them with the kiddos.
I have been doing the strength training exercise for over 60 days now, and I have noticed a big difference - most notably in my legs, posture, and balance. More than anything, I would say the Wii Fit Plus works on improving your balance. I have gained about 5 pounds of muscle in my legs - which is exactly what I needed - while losing pounds of fat around my waist. I have always had a V shaped upper body with skinny weak legs and a flat butt, but after 2 months my legs and hines are possibly as strong as they have been since college. I work out every other day, and I have yet to lose interest. One exercise - the single arm lift - was such a beating at first, that I thought I was going to give up all together. But now I pop right up like a spry teenager. I think I even walk different now. I have just started to supplement the Wii Fit with a few dumbbell exercises - incline bench, curls, and shoulder lifts - for a little extra girth in the upper body for swimsuit season (the Wii tends to slim down and tone, not build up). I have not even tried the yoga yet, but I may in the next few weeks.
We ended up purchasing several more games now to utilize the balance board, although none utilize it as well as this game IMHO. We recently purchased the Sports Resort which is also getting alot of play time from the kids.
We also just bought another Wii and WFP with board for my wife's parents, and plan to get one for mine since they have so much fun playing it...