Today's Inside Higher Ed has a brief article on the use of click-response technology in the classroom.
I've used them once, during a recent guest presentation to a general chemistry class of 140 students, most of whom did show up in class that day. I'm still ambivalent about them--the clickers, not the students--because I'm not sure they're as useful as their proponents claim. I do have to say, though, that they provided a pretty good snapshot of whether students got what I was talking about. What they didn't tell me, since I hadn't tested student understanding prior to the presentation, was how many students came in already knowing what I was talking about. That, unfortunately, would have taken more time than was available.
We're also working on a project on my campus that uses clickers in a plagiarism prevention workshop, adapted from such a workshop developed and presented elsewhere. We haven't piloted it yet, though.
My tentative conclusion is that they're useful but not revolutionary, and by themselves simply present another option. I prefer more hands-on and less lecture in my workshops, and class discussion when I can get it. I can see clickers' applicability for some types of library instruction, though.