"Personally I rail against this type of copy. You could say it ‘insults the intelligence’ of those who read it. On the other hand - we had great feedback from the course content and ultimately higher signups to our newsletter.
I want to have more people engaged with Piehole and I want to have more people come along to our courses. I wonder can softer copy achieve the same results?"
I think it can, James. I think there's a happy medium that employs some of the heightened tone and confidence of the killer copy approach but goes for passion rather than hysteria. I think you'd be right (for most products) to be less optimistic about converting into customers the kinds of people who respond to "Act before midnight" tactics than in those who consider more carefully what they are signing up for.
But, hey, maybe 300 million people CAN'T be wrong!