Perhaps you've seen it already but there is a video out there of the inventor carefully putting his finger into the spinning blade and the sure stop firing. Don't think I'd be prepared to do that but if he's willing to good on him.
What struck me about the sure stop demonstrations though (and the finger one in particular) was the way they didn't mimic what I see as the reality of a lot of really serious accidents - those where people slip / fall into the blade. You're hand is moving a lot faster in an accident situation than it is in those demonstrations. I'd love to see what happened if they threw a sausage at the blade, I bet it doesn't come away with just a scratch then.