Wii Fit sounds interesting to me, and I'm not a soccer mom living in Orange County... just a guy in his late 20s with a slightly developing beer gut that this may be able to rein in. Hooray for me being part of the new target demographic, suckers! I'm happy to see Nintendo continue to take the big risks, even if sometimes those efforts may have initial detractors or even turn out to be flops. How can you progress if you're not willing to go out on a limb first? Everyone else can just keep developing the same old shooters, I'm happy to have Nintendo continue to push for new and original content and concepts.
I would recommend renting it first if at all possible... I have it out rented right now myself. It's fun, but I doubt I would drop full price on it to own it (I'm also assuming that, after beating it, it wouldn't have a ton of replay value).