I briefly tried, but was unable to invest the time into it that was needed. From some other folks I've heard who have done it, it's a pretty drawn out process. Definitely a cost savings, but not so much a time saver. The other issue/question I have is whether or not you are able to save annotations, etc like you can on the other IWBs on the market. Additionally, part of the draw of most IWBs is the software package which comes installed to make use of the function of the board. I'm not sure if you get the same functionality from the Wii Whiteboard or if any of the software packages are available to those who don't own one of the marketed IWBs. Just some food for thought...may have to give it another go just for the fun of it.
Here is a link to a blog article which includes some links to programs to use with it (which I think Todd was referring to as a reason that it might not be a useful way to do things.)