For the first time ever I purchased a video game (if you can call it that) last week on the day it came out. While I have not been religiously devoted to Wii Fit since then, I do feel like it has staying power. The balance games are infuriating overall and I'm never quite sure I'm doing the exercises entirely correctly, but overall the workout is good and easy. Even the goofy "running in place" turns out to not be so goofy.
The key to Wii Fit is that it takes all of a minute or two to start "training." I just pull the Wii balance board out, turn on the Wii, navigate through a few menus, and off I go. Some people have expressed some frustration at the "navigating through a few menus" part. This is understandable, but I believe that choosing between workout allows for better pacing.
Wii Fit does not seem to come with a workout plan and users are mostly left on our own. There are a few "paired" exercises that I've found that work related muscle groups. The game tells you when you have done half of a pair and then tells you what the other exercise is. However, there is no daily/weekly/monthly program.
Although I have not unlocked everything yet, there are a few things I particularly like and don't like. The push-up/plank and jackknife exercises seem to be enough to work those muscle groups. The hula-hooping is surprisingly aerobic, at least for my current fitness state. As I mentioned earlier, some of the balance games are enfuriating.
Here are some interesting links: