I stumbled across this blogpost regarding a fairly new class-polling application called Socrative. From what I can tell, the application works along the same lines as the "clickers" for the SMART Board. The one major difference of course being that Socrative is a free app that utilizes students' personal laptops, tablets, and / or smartphones as the response device. On its face, technology of this nature seems like a great idea for gauging students' understanding of certain concepts. However, I'm still on the fence about it. I mean, really, what's simpler than having students raise their hands? I use to do it when I was a student, and I'm sure everyone else on these boards did the same. On the other hand, I can also understand the confidence that responding anonymously can give to a student. It allows him or her the opportunity to not have to worry about being ridiculed for not understanding a concept.
In any case, my question is this: Has anyone here used any of these types of immediate response systems? Can anyone attest to how practical such devices really are? Most importantly, do your students like them?