I work for a video game review site, and was in LA for the launch of the Wii at E3, and got one on launch day. In fact, before launch day, I wrote one of the first true hands on reviews in the country on the Wii while covering the Nintendo Fusion Tour back when it came out.
I finally picked up a WiiFit this past week when I got a review unit from one of our other writers, who wasn't using it much.
Anyone who thinks the Wii isn't excellent for working out isn't using it right. Yes, to be more successful in the game you need to do more wrist snapping than full arm movement (for now, Nintendo has announced an attachment to the Wii Remote that will make it far more accurate that will ship later). But, in Wii boxing for example, you can throw that wrist snap at the end of a full arm punch.
The WiiFit is a great workout to mix in with all of your other workouts. Because of the weather, I've been mostly trapped inside the past few days for workout purposes, and since I don't have a trainer yet, it's been the treadmill, the eliptical, and WiiFit. The WiiFit has a pretty big assortment of things to do, especially if you take them seriously. I have pretty good lower body strength, but not great upper body strength, so the pushups really punish me. The Yoga is way harder than I would have ever imagined (which is probably why every chick I know who does yoga is in the top 10 of my favorite hot chicks i know), and the cardio is a decent workout, even before you unlock the more advanced exercises.