We were off to a pretty good start in the first couple of days -- but be warned, you do need plenty of space where you intend to work out, especially as you get started in the strength training. We were a little surprised at just how much space was needed at times, so unless you've got plenty of it you may end up like us, spending plenty of time shuffling and reshuffling the balance board back and forth.
Players (exercisers?) are rewarded with more reps and new routines as they log hours, and if you're unfit (like we are) even some of the beginner exercises will undoubtedly reveal all those atrophied muscles (especially the push-ups / side-plank and jackknife routines, which are killers). Wii Fit's use of a plain, clearly visualized trainer makes learning the exercises -- and even the more complicated yoga poses -- easy for newbs. More after the break.
It only took an hour or two of doing the same routines before all the helpful input from your virtual trainer became tedious and repetitive. You can only hear your trainer say "Visualize the muscles you want to work" so many times, you know? You'll also be spending about 1/3rd of your total time in Wii Fit trying to get through a seemingly endless string of menus, intros, prompts, and requests to step on or off the balance board -- the reward for your patience is to initiate the next exercise.
Another big downer is the inability to play your own music. Wii Fit is clearly intended to be an accessible solution for people that haven't made fitness a part of their regular routine, so you'd think the software would be as accommodating and painless as possible if it's going to get people off the couch. Not being able to play music wouldn't be nearly as vexing if you could just turn down the monotonous Wii Fit music so you can play your tunes on a boombox or something, but you can't really mute the whole thing because the trainer does give some valuable real-time verbal feedback (like letting you know your balance is off, or that you're almost done).
As for our consistency in keeping up the exercises, well, it hasn't been great. We've logged a number of hours, but it's already becoming hard to see working in Wii Fit when the workouts themselves seem so encumbered by the software that delivers them. Although we're clearly working some unused muscles, we're not yet getting the feeling that the Wii Fit's burning any substantive amount of calories (or fat), or that it's any substitute for hitting the gym with some regularity. There's sweat, but it's not coming in buckets. We'll keep at it though, so check back in a few days for our next update.