I only heard Stephen Schneider speak once, about two years ago at a conference for journalists on climate science, in Portland. I mostly remember his sense of impatience (and a bit of anger) at the world's continuing doubts about a human influence on climate.
Here's one of the last interviews from him, from an alumni mag at Stanford. Schneider was extremely concerned about the recent tone of the debate over climate science, especially since ClimateGate -- in fact, he worried that a climate scientists might end up murdered. (Personally, I don't think this is an idle concern.)
His voice, and his frustration, will be missed.