I'm generally brimming with confidence when I release a demo. No, maybe it's more like, I'm breathing a sigh of relief, because I consider that section of the game "done". At least until the feedback comes!
What makes me nervous, though, is LPs/LTs. I managed to sit through two LPs/LTs, and they were both nerve-wracking experiences for me. I don't think I can really explain why, though.
*Edit: I vaguely recall speaking to unity about this some time ago in regards to when Fidchell switched his thread from text-feedback to video-feedback. I'm not going to deny how physically seeing players play a game is a highly valuable form of feedback. It's just... hard to watch?
*Edit2: I'm not making any sense, am I?