Ask HN: Is a survey a good way to get user feedback?

I run a startup web app and I am looking for more feedback on what current users like, dislike, if they share it with friends, what they'd like to see implemented etc. Is a survey a good way to accomplish this or should I take another approach? I already have a feedback button on the site but I think the feedback it captures is only a small segment of my user's thoughts. If I do a survey, which users (heavy, light, new, old, all) should I send it out to and what other questions should I ask? Does anyone have a survey already prepared they'd be willing to share? - Thanks