You should have better luck finding them since it's after the Holidays. We lucked into finding one before I had even had my Wii shipped to me on the shelves at Wal Mart. I think that's the only time I've seen them there, though. I have seen them at Costco and Best Buy, though, but they do go fast!
I haven't actually lost weight on it because I was real good about doing it for a couple weeks and then the hot water heater started spewing water and everything in storage ended up in the living room, and then it was the holidays, and now it's now, so I need to start doing it again.
I really liked it and was actually pretty good about doing it (until there wasn't room for it).
One of the big things with MS is that your balance gets off (sometimes if you see someone who looks like a drunk walking, they may just have MS and can't control it...unless they're coming out of a bar, then they're probably just drunk!). A lot of people on the MS board I'm on love it because of the balance exercises. Of course, Wii tells all of us that we're off-balance, which we already knew, but it does help to concentrate on those skills.