I have used the clickers several times, texting their names, answering questions in science,and math.  The students are very engaged and it gives me a "guick" view of their understanding.   I have to admit, I have been shocked a few times when they were "off the mark" and I really thought they were on track.

My challenges are - saving my questions after I have written them - I must be doing something wrong, go figure, but I have spent lots of time writing and then not being able to find them.