It's one of those polish-related features that aren't really a selling-point, but appreciated by the user when he finds it. That is, Nintendo wouldn't sell many more Wii systems by saying it has a DVD-player where you can navigate menus with the pointer (like with PC DVD playing software), but it would still be a neat part of a larger package.
I would have used the feature a couple times, since the TV cabinet in my room is too full to have a DVD player installed, but it's not that big of a deal.