They're buggy, gimmicky, overpriced pieces of crap. Or at least the models a few years ago were, they may have gotten better in the meantime.

SMART makes a ton of money in the education market, and we had about a dozen at my high school. The touch controls aren't sensitive or precise enough, the model of projecting onto a separate touchscreen means that it has to be recalibrated constantly, and the only software (SMART's drawing software) that takes advantage of the functionality has almost no features and still manages to have a horrible UI. No teacher used it for more than two or three lessons.