I finally got our Mimio boards working this week and I have to admit they are far more useful than I expected. They had about as much appeal to me as tablet PCs used to, and, frankly, I bought them because the state told us we needed to be using them, not because I thought they had too much value.
True smartboards are basically giant touch screens that look great in a corporate boardroom but whose $5000+ pricetags make them a tough sell in public schools. Our "interactive whiteboards" from Mimio, however, seem to be a nice compromise. They are full-blown whiteboards, so they can be used standalone with any dry erase markers. They can also output everything you draw to a PC or Mac (I haven't found any Linux hacks yet) using special covers for the dry erase markers.
They can pick up a variety of colors and their resolution is quite good. The Mimios can also be used in conjunction with a digital projector to redisplay any of your captured whiteboards. Thus, it's possible to go back several steps in a lecture and re-project the contents. What my students have found most valuable is the ability to post a series of whiteboards from a lecture on the web for later reference. The software that makes all of this happen is quite intuitive, as well, making for easy publication in a variety of formats (including complete website corresponding to a given lecture and standard image formats).
There is a bit of a learning curve to manage the computer, projector, and just give an effective lecture. However, for those of us who still favor a whiteboard over PowerPoint shows (or like to use both), interactive whiteboards offer a nice way to provide students with lecture notes online and revisit items in class.