The sooner you get paying users, the better, because then you can figure out what they really want and move in that direction.

Depending on what kind of users you have in mind, HN may or may not be a good place to find them. There are plenty of products, like patio11's stuff, that probably don't convert at all from HN since we're not his target market. Maybe find a niche and concentrate on that?

I'd just use email or the phone for feedback.