Being in the UK, Ive had my Wii Fit for 3 weeks now and it is fun, I have never regretted dumping £70 (approx $140)... well £63 (approx $126) for using the evil plastic (credit card).
The Yoga and Muscle Workouts were a challenge for me. I used to play football (round ball variety) for between 6 to 10 hours per week up until age 18 when I was hit with some knee problems. Generally speaking, Id class myself as unfit, tall and slim built. The Yoga will definately take time to master.
Balance Games are really fun. The first few times I tried, I really really sucked but once you learn how the Balance Board responds to your movements and the game plays out, they become a fun challenge. Trying to beat your score becomes obligatory and you will find yourself replaying and replaying just to get that little bit further or little bit better.
Aerobics... Hula and Super Hula are crazy. Id recommend doing this alone as if you dont look like a total idiot.... you probably arent doing it right. The Jogging is really good, gently breaking you in with 3 minute sessions until you unlock the 6 minute, the 10 minute island lap and then whats known as the Free Jogging where you can do 10, 20 or 30 minute sessions. The Step-up's are currently what I'm addicted to and its awkward for me. I seem like an uncoordinated clutz every time the pattern changes, this is however improving. The Rhythmic Boxing is possibly the most fun out of the lot despite it being awkward (for me) to memorise the short patterns.
Simply my 2 pennies or 4 cents worth...