I'm a lecturer and I think clickers are great, for large classes especially. Clicker questions and small group discussion about the answers gets students thinking rather than just sitting there with eyes glazing over. It works well. By giving a small amount of real credit to the answers you even get all the slackers discussing the topic and arguing about which answer is right.

Technologically clickers are impressively easy to use as well, you just need to put in slides with questions into the main presentation. The biggest disadvantage is students who forget to bring their clicker or have endless excuses about why they couldn't be in class on a certain day.