I have seen really good learning and teaching carried out with these. And I have seen these, unused and abandoned.
A study called "New Technologies and Educational Leadership: Missioners, Tentatives and Luddites: leadership challenges for school and classroom posed by the introduction of interactive whiteboards into schools in the United Kingdom" (2001) carried out by Derek Glover and David Miller, both from the Department of Education, University of Keele, Staffordshire, U.K, was interesting to read because it painted a very mixed picture on take-up of this expensive resource.
They concluded that many teachers saw it as small-scale change with "little compulsion for its adoption or use and with perceived limited impact on teaching methodology."
Increased adoption depended on what they called missioners and the conversion of tentative heads to believers.
There is such potential here. And problems to solve.
The projection is a problem - hot, often with the teacher causing a shadow on the screen with the older conventional throw projectors, and very poor image in any normally lit room (particularly in the tropics).
Resources are improving. This is important because the production of visually satisfying resoures is time-consuming.
And it is easier to do what one has always done.
I still think that large flat panel screens with interactive surfaces are better, even though I have yet to see this being used effectively in the classroom.