Due to my limited experience, I have only come in contact with SmartBoards. I had hear of one other system - Promethean - but I had never seen one (still haven't). Because of this limitation, it took quite a bit of research to figure out what the differences are between them.
I have used my SmartBoard in a variety of ways. Class announcements have been posted for all to see. I use my document camera to show students how to use calculators and multi-meters. The Smart Response system is great for teaching an interactive lesson.
It was nice to see that there are other systems out there. At this point in time it doesn't seem likely that I will ever have much chance to use them. This is one are of technology where I am limited to using what is supplied for my classroom.
