Has Anyone Ever Used Socrative or the SMART Board "Clickers"?

Hi Everyone,

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?